freelancer

crt lcd

2012-08-07T05:24:00.000-07:00

CRT is still better. CRT provides better sharpness and color than any flat panel technology. However, there's a limit to how large you can make a CRT due to the sheer weight of the screen - I bet that 32" CRT requires two people to move it since the screen alone probably weighs upwards of 100lbs, right?

2. All HDTVs (regardless of type) will automatically upscale (sort of like a "stretch") an incoming picture to its native resolution. This means if you have a 1080p TV, for instance, any incoming picture will be stretched to 1080p. Non-HD TV channels are only 480i, which means at any given time the TV only has 240 lines that it now has to stretch into 1080. While some TVs have a better upscaling processor than others, the fact is you're still asking the TV to basically guess at 80% of the picture - which is just going to result in a less distinct, fuzzy picture. (if you've ever displayed a photo on your computer and then tried stretching it to fit your entire screen, this is pretty much what your TV is doing.)

What you can do: Even without a HD cable box, your TV should be able to receive some HD channels - such as your local ABC, CBS, NBC, etc. in HD. Have your HDTV scan for channels. Any channel ending with a .1 is generally a HD channel. Also the channel's logo will say "HD" on it. If it doesn't say HD it isn't! Trust me, you'll know when you find a HD channel - it'll put your CRT to shame.

Note that if you want things like ESPN in HD, you will need to get a HD cable box from your provider.

1 Introduction

These pages compare CRT and LCD display technologies as rationally and scientifically as possible within the constraints of a domestic environment. They were prompted by repeated postings with no supporting evidence, in news groups such as uk.tech.broadcast and uk.tech.digital-tv, that CRTs are superior to LCDs, whereas my own experience is precisely the opposite. Where possible I supply or quote objective or independent evidence, otherwise I report my own experience, accepting that, unlike evidence, my experience is simply hearsay to others.

The sources of questions and criticisms mostly fall into two groups:

    Domestic users;
    Broadcast professionals.

Domestic Users

Either they are researching buying a new TV, in which case these pages may help, though primarily I would recommend Choosing A TV, or else are seeking further explanation as to why such a purchase, perhaps made after inadequate research, hasn't turned out as well as hoped.

With the latter, a typical scenario seems to be that a former analogue narrow screen (4:3 aspect ratio) CRT, which was aging before it broke and therefore had possibly drifted out of adjustment, is replaced with a much bigger wide screen (16:9 aspect ratio) LCD. Because of a combination of …

    The old TV had got out of adjustment;
    The new TV is significantly bigger than the old one;
    Analogue signal faults on the old TV are understood to be faults in the signal, but unfamiliar faults in the digital signal on the new TV are incorrectly ascribed to the new TV rather than the signal;
    Noone's bothered to look in the new TV's manual and menu options to discover how best to set it up;
    Being new, the TV is examined critically for the first time in ages;

… defects are visible which previously were not, and the new TV is blamed. In fact most, very probably all, will turn out to be in the digital broadcast signal - in the UK, digital signals are so over-compressed that only 1 to 3% of the original data captured by the camera ever arrives at the TV!
Broadcast Professionals

Typically broadcast professionals simply state, as assuredly as it was once claimed that the sun went round the earth, that CRTs are much better than LCDs. When challenged to supply supporting evidence, either none is forthcoming, or it is at best corporate hearsay, at worst pseudo-science.

The problem with corporate hearsay is that corporations have enormous inertia - a culture of jargon, work practices, standards, etc - that can be immensely difficult to change, and keeps them working in a certain way even though it may be shown to be based on a falsehood. Hence, for example, it is still common for people in the moving arts and visual display industries to refer to "persistence of vision" even though the concept was shown to be false as long ago as the 1970s1.

The most assured way of keeping abreast of new technology, and, a significant point, having an input into its design at an early enough stage for your industry to get what it requires of it, is to conduct trials. Strange as it seems to someone like myself of technical background, formerly employed to conduct such trials in furtherance of a firm's business, it does genuinely seem that noone has actually assessed LCD technology in such an independent, scientific, and rational way. Certainly, repeated requests have failed to elicit even a quote from the results of such a trial, let alone a full technical report, and repeated searches have failed to find any published results, even from 'open' organisations such as universities, technical colleges, the EBU, or the BBC.
2 Equipment Used

Naturally, I would have preferred to perform the sort of corporate trial discussed above, but this would have required access to a range of equipment that I do not have, and consequently, these documents can not and do not claim to be results of such a trial.

Instead, I have had to be content in making as impartial a comparison as possible using what I happen to own, being two ordinary televisions of similar size. To estimate how more widely applicable these results might be, I've spent much time searching for relevant data, completely without success for CRTs, and SD LCD data is also getting difficult to find now that HD is sweeping the market. The best that I can say is that while I have no reason to believe these TVs are unusual or atypical, they are probably not absolutely typical either, and one of each type is inadequate as a statistical sample. Hence, care should be taken in generalising from the following results!

Nevertheless, at least they are useful, demonstrable results, whereas, as far as I am aware, there is nothing scientifically robust coming from the pro-CRT side.

Unless otherwise indicated, the two televisions used were:
Type    CRT (aperture grille)    LCD
Model     Sony KV-16WT1U     Panasonic TX-15LT2
Size, Nominal Size (mm, in)     365, 14     385, 15
Screen Width (mm)     317 ±1.5     338 ±1
Screen Height (mm)     179 ±1.5     192 ±1
Measured Phosphor/Element Pitch (mm)     0.614 ±0.014, NA     0.390 ±0.014, 0.390 ±0.014
Calculated Effective Resolution     516 ±15, NA     867 ±35, 492 ±35

Notes:

    Ideally the televisions would have exactly the same screen size, the actual difference is roughly 5%.
    Neither TV has sufficient resolution to display SD at 720×576i - it's not meaningful to talk of vertical resolution with an aperture grille design, but the CRT's 72% horizontal coverage might be expected to lose picture detail more significantly than the LCD's 85% vertical coverage, and this is the most probable explanation for the results actually obtained favouring the LCD.
    The CRT has a scratch on the screen, but it does not feature in any picture fragment used here.
    LCD technology being much dimmer than CRT technology, in order to obtain adequate exposures, the LCD's Backlight and Brightness controls had to be set to their maximum values (in normal viewing they would both be at 50%). All other controls on both TVs were set for normal viewing, in particular all 'Artificial Intelligence' & signal processing options were disabled.

Photographs were taken by a Canon S40 camera mounted on a mini-tripod so that the lens was as near as possible opposite the middle of the screen, error < ±15mm, with a lens to screen distance of 300±5mm. The camera settings were:

    RAW image format
    Equivalent film speed ISO 400
    Shutter speed 1/100s
    Aperture F/8
    Manual shooting mode
    10s timed exposure delay (to eliminate camera shake)

Note that there are dead pixels in the camera, appearing as, mostly, red dots in some of the images here. These can be demonstrated to lie within the camera because they are always in the same pixel positions. As they have nothing to do with either television, they should be ignored.

The resulting *.CRW (Canon Digital Camera RAW file) photographs are each about 3-4Mb in size, but are not understood by web browsers, and hence have had to be converted via TIFF to PNG format of about half the file size. I did not discern any loss of detail in this conversion.

Composite video was chosen as the format for the source signal as this could be duplicated easily by a Quintro+ B-Tech BT945 SCART Switch via its two RCA composite video outputs. The TV2 switch on the unit was not depressed, and no channels were locked, which meant the TV1 and TV2 outputs were showing the same source signal.
3 Commonly Voiced Criticisms Of LCD TVs

Criticisms of LCDs that are commonly voiced include:

    Artifacts introduced by deinterlacing

    While it is known from the way CRTs work that most display each picture line as it is received, with LCDs there's a shortage of facts - it can be deduced from specifications that at least some recent High Definition TVs can deinterlace, but this appears to be an option selectable via menu rather than default behaviour; sources such as Wikipedia explain different deinterlacing methods2, and claim without convincing evidence that all non-CRT display types require deinterlacing3; others are more equivocal4:

        I've just had a very interesting chat with a guru within my company who deals with such matters. The short answer is that no one knows for sure how the processing is performed. You'd have to ask each individual manufacturer how they do it.
        …
        One thing is certain however, he has witnessed tests of many different types of screen all being fed with exactly the same signal. There are huge differences with temporal resolution, so the processing techniques are very different from mfr to mfr.

    Interlacing - LCD There is also this image which is from an interlaced analogue signal source displayed on my 22" LCD. If the LCD was deinterlacing it, you'd expect that lines would be paired, and that each pair would contain either identical content averaged over the pair, or interpolated content over the pair. Although superficially the lines look paired, they are neither averaged, individual lines in each supposed pair differ noticeably, nor interpolated, the edge of the person's arm in the upper line in each supposed pair seems if anything sometimes slightly to the left of the lower, whereas interpolation would place it about two pixels to the right, an unmistakable difference. Alternate lines also have a slightly different colour rendition. Hence, it seems that the picture contains two fields shown as such, and this LCD is not deinterlacing.

    In fact, I believe it makes more electronic and economic sense to assume that most LCDs buffer rather than deinterlace. To understand the difference between the two and why, the following must first be understood:
        Progressive Scan is when the signal or data representing a video image, here usually called a frame, is produced in a natural order, usually line by line top left to bottom right. This means that video content changes at the same rate as the frame rate, in the UK 25Hz. DVDs are mostly progressive scan.
        Interlaced Scan is when the signal or data representing video images is photographed as two fields, the first comprising odd numbered picture lines, the second even numbered lines, each field being produced progressively. This means that video content changes at the same rate as the field rate, in the UK 50Hz. Note the crucial point that the common description of interlacing as splitting a single video frame into two fields is only meaningful where video was originally photographed as progressive and is later interlaced, perhaps for broadcasting, but where the source is actually photographed as interlaced each field is shot 1/50s later than the previous one, and is thus independent of it, so the concept of frame has no meaning, and consequently this common description is misleading. Most legacy analogue video was photographed as interlaced, modern digital video can be either depending on camera settings.
        Buffering, in the context of video displays, is when part of a picture is stored until completely received before displaying it. In theory, either frames or fields could be buffered, similar circuitry could do for both, and likely could be switched into either mode depending on whether a progressive or an interlaced signal is being received. Note that buffering doesn't alter the video content or its rate, so, in the UK, a buffered display would still change the content of a progressive scan source at 25Hz and an interlaced one at 50Hz.
        Deinterlacing attempts to combine two successive fields from an interlaced signal into a single frame. Note that this assumes that once they were indeed part of a single frame as described above when a progressive source is broadcast as interlaced, which often will not actually be true, and that it alters both the received video content and its rate from, in the UK, 50Hz to 25Hz. For a progressive source being broadcast as interlaced, in principle deinterlacing can completely reassemble each original frame. However, if an attempt is made to deinterlace content that was photographed as interlaced, then deinterlacing would attempt to combine two independent fields into a composite frame, and the result will usually be worse than doing nothing at all to the picture.
    This being so, and deinterlacing circuitry being relatively complex and expensive, I cannot see why an LCD manufacturer would choose to increase the cost of its units by attempting to deinterlace the signal, when they have no way of knowing whether a given signal being displayed was originally progressive, in which case a slight improvement would result, or interlaced, in which case a significant degradation would result. It just wouldn't make economic sense. Some high-end LCDs appear to attempt it as a menu option, but I'd be surprised if the majority do it. I suspect that those sources that make these sweeping claims are actually confusing deinterlacing with buffering, a suspicion reinforced by the lack of any supporting evidence that stands up to logical examination.

    Jaggies

    It is claimed that LCDs show more jaggies than CRTs. Simply, this is a myth:
    CRT     LCD
    Jaggies - CRT     Jaggies - LCD
    Lack of contrast ratio

    I have satisfied myself that this criticism does have some foundation in fact, at least as far as my own LCDs are concerned, but the differences are only discernible in unusual situations - night time CCTV, some night scenes in B&W movies, star- and galaxy-scapes in astronomy or sci-fi programmes, etc. Further, CRTs commonly need adjustment of the Brightness to see such scenes optimally. What's really needed is a display technology with sufficient contrast ratio for this to be unnecessary, and neither CRTs nor LCDs are really adequate in this respect. Consequently, I do not intend to discuss this further here.

    Colour characteristics such as gamma

    As this is an issue for production rather than domestic environments, I shall not discuss it here.

4 Commonly Voiced Criticisms Of LCD Monitors

Criticisms of LCD Monitors that are commonly voiced include:

    Colour Rendition

    This shouldn't happen if monitor drivers are correctly installed. If required for correct colour rendition, monitors of any type should include an ICC Profile5 (*.icm) in their driver set. Perhaps those reporting this problem are not using the correct drivers, but instead general purpose drivers such as Default Monitor.

    Fonts - LCD Font Rendition

    In my experience this is a myth. Regardless of monitor type, the most critical factor for fonts is the aspect ratio of the resolution being displayed - if this is 4:3, fonts look fine, but the further it departs from 4:3, the worse they look.

    A subsidiary claim is that on an LCD fonts only look 'right' at its 'native' resolution, but a CRT has no such constraint. Again, in my experience, this is a myth - the native display resolution of my ViewSonic VG712s monitor is 1280×1024 (not even 4:3, which alerts the sceptic in me), but the accompanying photograph shows some text displayed in 1024×768, and there is no discernible degradation of the text. Besides the importance of having the correct monitor drivers, it is also necessary to have the correct settings under Start, Settings, Control Panel, Display, such as:
        Effects, Smooth Edges Of Screen Fonts
        Settings, Advanced, Monitor, Refresh Frequency
    For example, the default refresh offered is often 75Hz, which in my experience will usually display a picture on an LCD, but it is sometimes misshapen and distorted, while 70Hz is always excellent.

5 Health And Safety

    X-Radiation

    CRTs are inherently a mild X-ray source. Consequently, increasingly stringent standards for computer equipment have resulted - MRP-II, TCO-*6; I am not aware of any relevant international TV standards. Though nowadays the radiation doses given out are very low, they still have some significance. Those purchasing a new CRT monitor or TV may care to note that an average year of CRT TV watching is roughly equivalent to a year living next door to a normally operating nuclear plant7. This may seem trivial, but children regularly sitting for hours on the floor too close to a CRT TV or anyone constantly sitting in front of a CRT monitor probably represent significantly higher doses than average, and any X-ray exposure, particularly to children, seems senseless when it is entirely avoidable by using LCD technology.

    Eye-Strain

    There are hearsay reports of CRTs being more tiring on the eyes, to which their adherents often reply that the refresh rate was probably too low. In the absence, as far as I am aware, of conclusive and rigorous test results, I can only add to the hearsay. My experience is that refresh rate makes little difference above a certain level, probably somewhere between 50 to 100Hz depending on the individual, yet CRTs still tire the eyes above this level, whereas I have never noticed any adverse effects from using LCD monitors, even though on a daily basis I use them for hours without break. Further, I'd like to add the following …

    About a decade ago, I lost control over my immediate work environment for two years, and had to sit closer to my CRT monitor than I really wanted to - my eyes were probably about 0.5m or less away from the screen, whereas before and since I've always worked at 1m. During that time I would feel tiredness in my eyes within a short time of starting work, much sooner than previously. Also over that time my eyesight rapidly deteriorated to the point where I now need glasses to read small print. It could be argued that this was natural ageing, and I couldn't disprove that, but my own feeling based on the timing and rapidity of the deterioration is that the major cause was that particular desk layout causing the closeness of the CRT. By contrast, I've been able to keep the same glasses ever since I started using LCDs.

Compatibility Addresses

2011-10-28T00:37:00.000-07:00

Compatibility Addresses
To aid in the transition from IPv4 to IPv6, the following addresses are defined:
• IPv4-compatible address
The IPv4-compatible address, 0:0:0:0:0:0:w.x.y.z or ::w.x.y.z (where w.x.y.z is the dotted decimal representation of a public IPv4 address), is used by IPv6/IPv4 nodes that are communicating using IPv6. IPv6/IPv4 nodes are nodes with both IPv4 and IPv6 protocols. When the IPv4-compatible address is used as an IPv6 destination, the IPv6 traffic is automatically encapsulated with an IPv4 header and sent to the destination using the IPv4 infrastructure. IPv6 for Windows Server 2003 and Windows XP supports IPv4-compatible addresses, but they are disabled by default.
• IPv4-mapped address
The IPv4-mapped address, 0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z, represents an IPv4-only node to an IPv6 node. IPv4-mapped addresses are used for internal representation only. The IPv4-mapped address is never used as a source or destination address of an IPv6 packet. IPv6 for Windows Server 2003 and Windows XP does not support IPv4-mapped addresses.
• 6to4 address
The 6to4 address is used for communicating between two nodes running both IPv4 and IPv6 over the Internet. You form the 6to4 address by combining the global prefix 2002::/16 with the 32 bits of a public IPv4 address of the node, forming a 48-bit prefix. 6to4 is an IPv6 transition technology described in RFC 3056.
• ISATAP address
Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) defines ISATAP addresses used between two nodes running both IPv4 and IPv6 over a private intranet. ISATAP addresses use the locally administered interface ID ::0:5EFE:w.x.y.z in which w.x.y.z is any unicast IPv4 address, public or private. You can combine the ISATAP interface ID with any 64-bit prefix that is valid for IPv6 unicast addresses, including the link-local address prefix (FE80::/64), site-local prefixes, and global prefixes. ISATAP is an IPv6 transition technology described in RFC 4214.
• Teredo address
The Teredo address is used for communicating between two nodes running both IPv4 and IPv6 over the Internet when one or both of the endpoints are located behind an IPv4 network address translation (NAT) device. You form the Teredo address by combining the 2001::/32 Teredo prefix with the public IPv4 address of a Teredo server and other elements. Teredo is an IPv6 transition technology described in RFC 4380

c programming

2011-07-20T23:49:00.000-07:00

The C Programming Language Torn Apart

Introduction: The evolution and Description of C

The C programming language is a general purpose language which was originally designed for use on the Unix Operating System by Dennis Ritchie. The Unix Operating System, Unix Applications and Tools have been coded in C. This language has evolved from Ken Thompson's B language, which was the language designed for the first Unix System.

C is not a machine specific language and a C program can easily be edited to make it work on various platforms. After the creation of the C programming language, over the years, C became the most preferred language amongst programmers around the world. Due to its immense popularity, many companies developed their own versions of the C compilers, added new features and commands etc This resulted in no specific standard followed by the various programs and led to utter confusion amongst programmers around the world. A need was felt to introduce a standard machine independent code which would be followed by all and make life a lot more easy for programmers. So in 1983 the American National Standards Institute (ANSI) established a committee which aimed at doing just that. This series of manuals too is based on and follows ANSI standards.

C is a high level language. By that what I mean to say is that the C commands or code is written in code which is easily understandable by humans. Its commands are infact plain English words and symbols. As a result C is non machine specific. C is not an interpreted language and unlike Perl a C program has to be first converted into Binary code with the help of a compiler. A compiler does just what the name suggests, compilation i.e. conversion of human understandable code into Binary machine understandable code.

So, even before you can continue reading this manual, you need to get yourself a compiler. To compile C programs, even any C++ compiler would do. If you are a Windows user, then I suggest you get Visual C++, which is a part of Microsoft' s Visual Studio. Although it costs a lot, it is my favorite as it also gives you the benefit of using the MSDN Library. The other good compiler would be Borland C++ 5.5 (available for free download from: http://www.borland.com/bcppbuilder/freecompiler/ ) Then there is DJGPP which is available at: http://www.delorie.com/djgpp/.

If you are running any kind of Unix, then you have a C compiler in your disk itself. You see, the cc and gcc utilities are actually C compilers. For more details, read Carolyn's GTMHH on C, at happyhacker.org

The Standard C Header Library

The ANSI C standard library is an exhaustive collection of pre written routines or functions that are needed by programmers in various applications again and again. Without the functions and routines contained by the header files, a program cannot work properly. Now instead of including the entire code of a long header file in each program , we declare the header files used by the program and reuse the routines contained by them. To understand header files better, read on.

Let us take a practical example to see what actually happens when we try to display a string on the screen. Now to print something on the screen, without using any header file, we need to follow a very complex procedure. Firstly, we would need to extract the string to be printed from the program code, then look for the port in which the Standard Output device is installed, then send the string to that particular port, instructing the Standard Output Device what to do with the string. To write the entire set of above instructions in each C program we develop, would be really cumbersome and inefficient. That is why we use Header Files. With the use of Header Files, we can leave the coding of the entire above procedure to the Header File. With the use of Header Files, we no longer need to know how to communicate with certain Hardware, but instead simply need to know which routine or function to use. Header Files have a .h extension.

The following is a complete list of header files which are a part of the Standard ANSI library-:

Standard Input \ Output

Diagnostics

Character Handling

Errors

Characteristics of Floating Types

Sizes of Integral Types

Localisation

Mathematics

Non Local Jumps

Signal Handling

Variable Arguments

Common Definitions

Commonly used General Utilities

String Handling

Date and Time

NOTE: For the Time being, we are only concerned with the Standard I\O header file: stdio.h

Like in the Perl Manual, we will start with the obligatory Hello World program which simply prints the text: Hello World on the screen. It is a big step in a novice's programming career and a person gets immense pleasure if his first program works without any problems.

The following is the source of the Hello World Command. Before I analyze and explain each line of the program, study the program and try to figure out what each line does, then move on to my explanation and see how much you got right. Self Learning can go a very long way.

#include

main() {

printf ("Hello World \n");

}

Output-:

Hello World

Now let us analyze the code snippet. The first line tells the computer to include information or commands and functions or routines from the header file: stdio.h which is needed to do anything regarding

Input \ Output. The second line defines the function called main. The main function is a special function as it is this function, which by default starts automatically whenever a program is run. [NOTE: Other normal functions can be named anything we want them to be called. We will learn more about functions in upcoming manuals.] The empty brackets, the ( ), after main specify that the function main does not receive any arguments. A function contains certain statements or commands which are executed each time the particular function is called. Now, these statements are enclosed within curly brackets or braces. The '{ }'.

In our first example, the function main has only one statement.

So how does Hello World actually get printed on the screen? Well as soon as the function encounters the function 'printf', it gets the arguments contained by it i.e. the text within the brackets ( ). Then the program calls the printf function in the header file: stdio.h and passes it the values to be printed.

The '\n' is the newline character which causes the Output Cursor to move to the first column of the next row or line. Let us see an example to understand how the newline character works. Say, you want to modify your first C program such that it prints Hello on one line and World on the next line. Then the code would become:

#include

main () {

printf ("Hello");

printf ("\n");

printf ("World");

}

Output:

Hello

World

Well, actually the same could be achieved with a smaller piece of code:

#include

main () {

printf ("Hello \n World");

}

Get it? OK, now that you know what the basic structure of a C program is, let us learn some C routines in detail.

The printf Routine: Printing Stuff

The printf routine is a part of the Standard I\O Header file: stdio.h. It helps to display text, numbers and symbols in the specified format on the standard Output Device, which is normally your Monitor.

The general syntax of the printf routine is:

printf ("Characters", ARG1, ARG2…ARGn);

where CHARACTERS is the string to be displayed on the screen. It can have upto 3 distinct escape character sequences, [I have discussed them later in this section.] in any combination. The ARGn is normally a variable whose value is printed on the screen. Confused? Well the following example, ought to clear all your doubts.

Example:

#include

main () {

printf ("PIE=" , PIE);

}

Assuming that the value of the Variable PIE is 3.14, the output of the above would be:

PIE= 3.14

The following is a complete list of possible escape sequence characters which are a part of ANSI C:

\a Alert Bell

\b Backspace

\f Form Feed

\n New Line

\r Carriage Return

\t Horizontal Tab

\v Vertical Tab

\\ Backslash

\? Question Mark

\' Single Quote

\" Double Quotes

\ddd Where ddd is an octal number and represents the ASCII code for the number

\xdd Where ddd is a Hexa Decimal number and represents the ASCII code for the number

Examples:

printf ("Is this a VIRUS ALERT \? \a");

will print Is this a VIRUS ALERT ? on the screen and will sound a bell from the CPU Speaker.

printf ("Ankit \t Fadia \n Fadia \t Ankit");

will print the following on the screen:

Ankit Fadia

Fadia Ankit

Formatting your Output using Printf Options

This part might seem a bit weird to grasp, but I assure you, if you read the entire section, you will find it quite easy. You just need to try not give at half stage before reading the entire section.

The general syntax of the printf formatting option is:

%width[.precision] type

where width is the minimum size of the field in which the characters (Output) has to be displayed. It is the number representing the minimum size of the field for displaying the output. The output is right justified unless the width is negative, in which case the output is right aligned. The width does not truncate the output, but accordingly increases its size, to accommodate the output.

The Type can be anything from the below options-:

d, i Decimal Number

o unsigned Octal

x, X unsigned Hexadecimal

u unsigned Decimal Integer

c Single Character

s String

f Floating Point Decimal

g, G Floating Point Number in either fixed decimal or exponential form,

e, E Floating Point Number in Exponential Form

And the precision is the number of places which the output numeral of the Type will have. Like I said before, all this would definitely sound a bit too overwhelming for a complete newbie, but stick with me and keep reading the following examples and I assure you, all your doubts would be cleared.

Examples:

printf ("sum = %10d \n", result);

if the value of the variable result is 145, then the output will be:

sum = 145

In this case, due to the format options we gave, the C program assumes that the value stored by the variable result is a decimal Number [Specified by d] and displays the output i.e. the vale of the variable result in a field of 10 characters wide. [ Specified by %10]. As the width in this example is positive, [10] the output is left aligned. Now let us say if we change the above line of code to the following:

printf ("sum = %-10d \n", result);

then everything else remains the same, only the output instead of being left aligned, is right aligned.

printf ("Percentage = %10.3f", percent);

Assuming that the value of the variable percent is 2.345, the output will be:

Percentage = 2.345

Let's take a bit more complex example which includes escape Sequences.

printf ("\t%2d:%2d %c \n", hours, minutes, time);

Assuming that the value of hours is 11, value of minutes is 45 and the value of time is PM, the output would be:

11:45 PM

Consider the following example:

printf ("%s \t %6.2f \t", item, price);

Assuming that the value of item is CD and the value of price is 100.25, then the output would be:

CD 100.25

Well, till now I am sure almost all of you must be clear in your mind, as to how the printf function can be successfully used. However, if you still have any questions, feel free to contact me.

Gathering Input: The scanf( ) routine

Just like we have the printf( ) function to display output on the screen, we have the scanf( ) function to gather input from the user and to add interactivity to our programs. Before I move on to the syntax and other information on the scanf( ) routine, you need to understand the difference between a variable and the memory location of a variable.

You see, whenever we declare a variable, the C program keeps a part a specific part of the memory for it. Now say we declare a variable and name it ankit and give it the null value i.e. nothing. Now when we give the following print command:

printf ("Ankit's value is: %s", ankit);

then the output would be:

Ankit's value is: NULL

Remember that the variable ankit has been assigned a memory location to store whatever value we want to assign it. Right? Well to refer to this memory location set apart of the variable ankit, we need to make use of the address operator i.e. the & operator. So giving the following command will print the memory address assigned to the variable ankit:

printf ("%s", &ankit);

Now that you know when the address operator is used, let us move on to the basic syntax of the scanf command:

scanf ("Specification", addresses);

where specification is a set of rules which decides the kind of input the program expects the User to type and addresses is a set of memory locations to which the Input is to be stored.

The specification part is nothing but the formatting options which the printf( ) routine has. It decides whether the program is looking for decimals, floating points or characters as input. It also decides the maximum number of characters which can be accepted as input. Basically the syntax of Specification is as follows:

%[width] type

where width specifies the maximum number of characters which can be accepted as input. If the User tries to input more number of characters than specified by width, the program does not accept them and the input cursor does not move ahead.

Type can be anything from the following list of values-:

d, Signed Decimal Number

i Signed Integer whose base(Type of Number System) is decided by the format of the number input:

If the prefix is 0 it expects an octal integer

If prefix is 0x then it expects a Hexadecimal Integer

Else if there is no prefix, then it expects a decimal integer

c Character

s String

o unsigned Octal

x, X unsigned Hexadecimal

u unsigned Decimal Integer

e, f , g Signed Floating Point Value

l This is used to prefix e, f, g and signifies a long integer or unsigned long integer

L This is used to prefix e, f, g and signifies a long double

Let us take some examples to make this routine clearer.

Examples:

scanf ("%d", &pie);

will take a decimal from User Input and store it in the address of the variable ' pie '.

scanf ("%10s", &name);

will take the first 10 characters from the User Input and store them in the address of the variable ' name '.

scanf ("%d%c%lx", &dec, &stringvar, &longvar);

will take a decimal integer, a single character and an unsigned Long Hexadecimal number and assigns them to the addresses of the variables dec, stringvar and longvar.

NOTE: Please, note the Address Operator before the variable name in each of the above examples. Without the use of this operator the program will not work and the variable will not be assigned any value. Somehow, we do not need to use the Address Operator while printing the value stored by a variable. Just remember that while using scanf, you need to use the address operator and with printf, no address operator needs to be used. There is no need to go deep into the reasons behind this.

Wasn't that easy? Well C is not as difficult as it is projected to be and I am sure all experienced C programmers agree with me on that fact. Anyway, till now we have learnt how to print the value stored by a variable and also how to get input from the user and assign it to a variable. But, these routines are of no use if we do not know how to declare variables. In C, we cannot declare and assign values to variables at the same time. You need to first declare a variable and only then can you assign it a value. So let us know learn how to do just that.

Variables

In C, all variables must be declared before they can be used or assigned a value. Variables are usually declared in the beginning of a function i.e. before any executable commands or routines start. A variable declaration is of the following format:

Variable_Type Variable_Name

where Variable_Type is the type is the type of variable, which symbolizes the type of data stored by the declared variable(int, char, float etc) , and Variable_Name is the name of the variable being declared.

A typical variable declaration would be:

int number;

The above line declared a variable by the name number and declared it to store an integer. We can declare more than a single same type of variable in a single line:

int number, number1, number2;

This line declares three Integer variables: number, number1 and number2.

C supports the following basic data types:

int Integer

float Floating Point (Numbers having a fractional Part)

char Single Character (Single Byte like a, b, c etc)

short Short Integer

long Long Integer

double Double Integer

NOTE: The range of int and float varies from system to system. And these are not the only kind of data types. We still have arrays, pointers, structures etc which we will discuss later.

Now, that we have learnt how to declare variables, we need to know how to assign values to them. Well, to assign values to variables, we use the assignment operator, i.e. The ' = ' operator.

For example,

int number;

number = 20;

declares a variable by the name number and type Integer and then the second line assigns it the value 20.

My First Useful Working Program

Now that we know a bit about I\O and also a bit about variables, we are in a position of creating out first useful working C program!!!. This program will ask the user to type the temperature in Fahrenheit and will convert it into Celsius and print the result on the screen. However before we move on, we need to cover a tiny detail: Comments. Anything between a ' /* ' and a ' */ ' is called a comment and is ignored by the compiler. They are inserted so that people find it easier to read the code and understand what each line is meant to do. The following example, has a lot of comments.

#include /* Include the Standard I/O Header File */

main() { /*Start the Main Function, which is executed automatically */

int fah, cel; /* Declare the (int) variables which will hold the Fahrenheit and Celsius Equivalents */

printf ("Enter Temperature in Fahrenheit:"); /* Hello User. I am hungry, feed me a value */

scanf ("%d", &fah); /* Get the User Input and store it in the address of fah */

cel = (Fah -32) * 5 / 9; /* Get the Grey Cells Working, convert input to Celsius */

printf ("\n \n Temperature in Celsius is….%3d", cel); /* Give User What He wants */

}

Output:

Enter Temperature in Fahrenheit: 32

Temperature in Celsius is…. 0

Wow!!! Wasn't that a kewl program? Well, at least a kewl enough for a C newbie. Anyway, now we come to the Examples Section of the Manual, which consists of a collection of important examples, which make life easier for a newbie C programmer by helping him to learn better. Also comments have been provided where ever necessary.

The following example illustrates the use of all kinds of data types with the printf( ) and scanf( )routines.

#include

main() {

int inum;

float fnum;

double dnum;

long int lnum;

printf ("Enter An Integer:");

scanf ("%d", &inum);

printf ("Enter a Floating Point Number:");

scanf ("%10f", &fnum);

printf ("Enter a Double Value Number:");

scanf ("%le", &dnum);

printf ("Enter a Hexadecimal unsigned Integer:");

scanf ("%le", &lnum);

printf ("inum = %-5d\n", inum);

printf ("fnum = %10.4f\n", fnum);

printf ("dnum = %15.4e\n", dnum);

printf ("lnum = %lx \n", lnum);

}

Output:

Enter An Integer: 123409

Enter a Floating Point Number: 1.546789

Enter a Double Value Number: 9.879054678E-15

Enter a Hexadecimal unsigned Integer: B543

inum =123409

fnum =1.546789

dnum = 9.879054678E-15

lnum = B543

Remember that I told you that the float and integer value ranges differ from system to system. Now the following program demonstrates how to get and print these ranges. All these ranges are given in the and header files, so we need to include them too.

#include

#include

#include

main() {

char char_min, char_max, char_unsigned_max;

int int_min, int_max, int_unsigned_max;

long int long_int_min, long_int_max, long_int_unsigned;

float float_min, float_max;

double double_min, double_max;

char_min = SCHAR_MIN;

char_max = SCHAR_MAX;

char_unsigned_max = UCHAR_MAX;

printf ("Char Min: %d\n", char_min);

printf ("Char Max: %d\n", char_max);

printf ("Char unsigned Max: %u\n\n", char_unsigned_max);

int_min = INT_MIN;

int_max = INT_MAX;

int_unsigned_max = UINT_MAX;

printf ("Int Min: %d\n", int_min);

printf ("Int Max: %d\n", int_max);

printf ("Int unsigned Max: %u\n\n", int_unsigned_max);

long_int_min = LONG_MIN;

long_int_max = LONG_MAX;

long_int_unsigned_max = ULONG_MAX;

printf ("long Int Min: %ld\n", long_int_min);

printf ("long Int Max: %ld\n", long_int_max);

printf ("long Int unsigned Max: %lu\n\n", long_int_unsigned_max);

float_min = FLT_MIN;

float_max = FLT_MAX;

printf ("Float Min: %15.9e\n", float_min);

printf ("Float Max: %15.9e\n\n", float_max);

double_min = DBL_MIN;

double_max = DBL_MAX;

printf ("Double Min: %25.16e\n", double_min);

printf ("Double Max: %25.16e\n\n", double_max);

}

printable

2011-07-11T00:31:00.000-07:00

aha

2011-07-11T00:15:00.000-07:00

Audio

2011-03-15T03:59:00.000-07:00

Buy Now!

Jays delivers a smooth-sounding on-ear headphone that gives you three ear
cushions to customize your listening experience. Although they don't come
cheap, the c-Jays are a worthwhile investment if you're shopping for an
aftermarket pair of on-ear headphones to fit your mobile lifestyle.

Buy Now!

The Jays A-Jays Four earphones provide a well-balanced sound and a polished,
utilitarian design that make them excellent replacement earphones for your iOS
device.

I just want reality to sound a bit more like science fiction ...

Buy Now!

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The new HD 598's "wow" styling updates the classic Sennheiser look, and the
sound has more detail and higher resolution than previous models. We recommend
these cans to anyone looking for a pair of headphones with precision sound
quality and a wide-open soundstage.

Buy Now!

Redbox, building on the success of their bright red DVD rental kiosks, has
announced that it will be expanding its rental of physical DVDs and will also
offer a subscription-based ...

Save 20% on SPAMfighter Pro. Buy now!

The Image One's bass outmuscles the competition and tight earcup seals hush
external noise. With a closed-back design, a solid two-year warranty, and more
lifelike sound details at half the price of competitive models, the affordable
Klipsch Image One well deserves our CNET recommendation.

Save 20% on SPAMfighter Pro. Buy now!

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The Audeo Perfect Fit Earphones PFE 022 + Mic are a solid choice for iPhone
owners who desire balanced audio and a light, compact design.

For someone who wants to DVR-ify an HD antenna setup without paying monthly
fees, the Channel Master CM-7000PAL is the easiest solution available.

Save 20% on SPAMfighter Pro. Buy now!

Google Acquisition Spending Spree (Venturebeat) -- Google is now on track to
acquire a new company every two weeks this year. (via azaaza on Twitter) Where
Good Ideas Come From (YouTube) -- this perfectly describes Foo. A Taxonomy of
Data Science -- great first post on a new blog by data practitioners. Rockbox
-- open source (GPL) firmware for...

Save 20% on SPAMfighter Pro. Buy now!

General Research of Electronics at the 2011 International Consumer Electronic
Show, intro's a radio scanner that is extremely easy to use. Consumers will
now be able to experience and purchase the GRE line of scanners at their local
retail stores.

OPPO has finally announced that its BDP-93 3D/Net Streaming Blu-ray Disc
player is now available for order. What makes this player different than most
others on the market?

In addition to 3D and NetStreaming (from services such as Netflix and
Blockbuster), the BDP-93 provides both SACD and DVD-Audio Disc playback as
well as compatibility with a host of other formats, including, but not limited
to, HDCD, MKV, DivX, and standard audio CDs. The BDP-93 can also play back
media files from connected USB Flash or eSATA drives. Of course, standard DVD
isn't left out. The BDP-93 features a Marvell QDEO Kyoti-G2 88DE2750 upscaling
chip which, if implemented properly, should provide excellent deinterlacing
and 1080p upscaling for DVD playback.

On the convenience side of things, the BDP-93 also provides Dual HDMI outputs
that enable the user to connect one HDMI output directly to a 3D-TV, while
using the second HDMI output for connecting a separate audio feed to a pre-3D
capable home theater receiver.

For all the details on the OPPO BDP-93, including photos of the video
processing board and chips, and pricing and ordering information, check out
the Official OPPO BDP-93 Product Page.

The Olive 4 is a fantastic-sounding digital audio server, but its high price
and limited feature list limit its appeal to die-hard audiophiles.

Food and home with hp, she will discuss shopping secrets with you that she has
found to be most effective when shopping for food.

TDK's Three Speaker Boombox is as beautiful as it is powerful, but the hefty
design does not travel well.

The Yamaha TSX-70 offers impressive features and sound quality, but the design
misses its intended targets: the bedroom and kitchen.
.

Securenet Systems announces a new song playlist widget that radio stations can
embed on their website. It shows what is playing now, artist, album, track
info, and the last songs played. There are buttons that link to artist videos,
lyrics, concert ticket sales, bio page, and ringtones, plus a link to purchase
the song on iTunes.

While it lacks integrated Wi-Fi and is more expensive than the Roku and Apple
TV , the WD TV Live Hub's combination of the snazzy interface and built-in 1TB
hard drive will appeal to advanced users who have a lot of existing files they
want to view on an HDTV or stream to other PCs on their network.

If you can look past its so-so sound quality on music, the impressively
flexible design of the Altec Lansing Octiv Stage MP450 turns your iPad into a
video monitor for bedside or kitchen viewing.

Arranging Things: The Rhetoric of Object Placement (Amazon) -- [...] the
underlying principles that govern how Western designers arrange things in
three-dimensional compositions. Inspired by Greek and Roman notions of
rhetoric [...] Koren elucidates the elements of arranging rhetoric that all
designers instinctively use in everything from floral compositions to interior
decorating. (via Elaine Wherry) 2010 Mario AI Championship...

printers

2011-03-08T23:11:00.000-08:00

Printers News

Printing evolved?

It's not often you see something a bit different in the printer/AIO market but
Lexmark has produced a device that should turn a few heads in the Genesis
S815. Most immediately striking are the aesthetics, since it utilises an
innovative vertical design finished with a sleek piano-black front panel that
also houses a 4.5-inch colour touchscreen.

Lexmark isn't going all "super-model" on us and focusing the appeal of the
S815 solely around looks however, as it boasts a "world's first" technology
called Flash Scan, which can allegedly scan images in 3 seconds, as well as
instantly previewing the page on the main display for adjustment. You'll also
find more typical conveniences such as wireless printing, a PictBridge USB
port, multicard reader, duplex mode and more current advancements in the form
of access to online content via the touchscreen display.

All of this sounds very good, but ticking the boxes in terms of key
performance is obviously a must. Sadly it doesn't cover all its bases here, as
we found print speeds to be far, far slower than the 33ppm quoted draft
setting. In our tests we found 8ppm to be more accurate; a significant ...

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The Epson WorkForce 60 is a bare-bones color inkjet printer. It has very good
print speeds at normal quality (and laser-like text at high quality printing),
with handsome prints and very good photo quality. Wireless 802.11n is built
in, as is a duplexer. Otherwise, you won't find any bells or whistles on this
Epson Workforce.

Want to turn your old snaps digital?

Cast your mind back to the days when Facebook didn't exist, DM referrred to a
boot rather than a direct message and no one had a digital camera. Remember?
Chance are that it's hard to forget, as you've probably got shoeboxes full of
old photos to remind, you. That's where the Veho Renovo photo scanner comes
in. This gadget lets you turn your 6 x 4-inch photo memories into JPEGs so
that you can file your nostalgic family prints away on your hard drive for
future generations or simply annoy your friends by posting dreadful, old
pictures of them on Facebook.

The Renovo scanner is pretty compact, measuring in at just 157.4 x 43 x 54.4mm
and tipping the scales at a lightweight 230g. The white plastic finish
actually looks fairly slick close-up, and the unit is reasonably sturdy too.
The feeding slot for the photos stretches across the front of the device and
it features a paper guide on the right to make sure that your photo fits
snugly. Next to the main slot you'll find the power button alongside an
indicator light that tells you whether ...

A closer look at Kodak's home printing price buster

Are you a mum in a photo active family? Are you mid-income with high
aspirations for your children whom you wish to be successful and creative? If
that's sounds like you, then you should be buying a Kodak ESP C-series inkjet
printer and, according to the company marketing meetings, you're also called
Fiona.

The Kodak ESP C310 and ESP C110 are both all-in-ones, minus a fax offering,
with the only difference between them that the former supports Wi-Fi whereas
the latter doesn't. All the same, they'll each allow you to print, copy and
scan to your heart's content.

The inkjets, launched at CES 2011, are spearheading Kodak's second big push on
their undercutting of the competition on ink prices over the last two years as
they hope to keep increasing their market share with the headline message that
Kodak inkjets are the cheapest way to go.

Consequently, what we got when Pocket-lint had a hands on with the pair was
something pretty simple. They're standard L-shape printers with the paper
going in the back end and coming out of the front so as not to confuse anyone
with ...

2/2/2011 3:10:00 AM

INTERVIEW: Company explains all

How expensive do you think it is to print a photo at home? While prices are
coming down, far too many of us believe that printing from home is something
that only the rich can afford.

"There's been a shift from home printing into retail printing - either online
or at at kiosk - and we think one of the reasons that's happening is because
getting a great photo from home is still too hard," director and vice
president of consumer inkjet Europe Bob Ohlweiler tells Pocket-lint. "It's
inconvenient and it's expensive."

With $45bn each year spent in the inkjet printing industry, you can see why
it's big business and a worry for companies like Kodak who make their living
from us looking to store our memories physically rather than just on our
computer or cloud services like Flickr. ?

That's not stopping Kodak though. The company has seen its share in the UK
printing sector rise from 6 to 10.5 per cent in the last two years and has
already started 2011 with figures of 14 per cent after it shifted its focus
toward undercutting the rest of the market on ...

1/28/2011 1:21:00 AM

Printer and Android tablet? Whatever next?

It's been well publicised that 2011 will be "the year of the tablet", and with
the new version of Android on the way, rumours of a new iPad gathering
momentum and a handful of capable devices doing the rounds at the moment,
there should be plenty of choice for those who want a larger device than a
phone to entertain themselves with come the summer. One thing we weren't
expecting to see was an all-in-one printer bundled with such a tablet, but
this is what HP is attempting with the PhotoSmart eStation C510.

At its heart an all-in-one device combing print, scan, copy and (online) fax
capabilities, the distinguishing feature of this essentially mid-range
offering is the inclusion of a detachable 7-inch screen running Android 2.1.
It's called the Zeen, and as well as offering a large display with which to
interact with the printer, brings access to a range of online and offline
content to either enhance the printing experience or provide you with some
additional benefits to keep you entertained around the home.

The Zeen offers access to a typical array of web-based content via its built-
in ...

Connected printing

HP takes another stab at the home all-in-one market with its new Photosmart
series, which includes the mid-range CN503b - a printer/copier/scanner inkjet
device that distinguishes itself from many rivals through the use of a
2.4-inch full colour touchscreen display. As well as offering intuitive access
to the key features of the product, HP is bringing its device into the modern
age by offering wireless access to a range of online resources directly
accessible through the panel, which include printable games, maps, colouring
pages, forms, templates, calendars and more. It also offers the ability to
print from afar using the associated applications and offers wireless access
to local networks which are easily configured using the straightforward setup
wizard?

First and foremost, the device's capabilities as an all-in-one are best
described as "above average". We liked the styling of the 503b and the
presence of a versatile photo paper tray that can handle up to 7 x 5-inch
photo paper, a 125 sheet main tray, 50-sheet output tray and the fact that it
can handle a wide range of media sizes means it's a decent all-rounder for the
modern home. HP's quoted print speeds of 11ppm ...

1/24/2011 2:08:00 AM

The Brother HL-4570CDW is a color laser printer aimed at businesses and
workgroups. It boasts business-friendly features such as fast printing, built-
in wireless, and automatic duplex printing. It also offers some consumer-
friendly features such as a USB port on the front of the machine, and an app
that will let you print directly from an Android smartphone.

Sexy hard drives, lots of Angry Birds and a sad day for photography in Kuwait

After the tsunami of gadgets that washed up on our pages over, well, the rest
of the year really, November 2010 was quite a pleasant time to take a closer
look at the few that were afforded a big launch that month - as well as some
of the sillier news stories floating around.

On the serious side, it was a chance for the mini-Micro Four Thirds that is
the Panasonic GF2 to star in one of our photo galleries along with the
flagship BlackBerry Bold 9780 and the take two from HP/Palm in the form of the
Pre 2. For those looking to burn money, Panasonic also brought out a ?65,000,
103-inch, 3D plasma TV and Harrods came up with a way to make the Galaxy Tab
even more expensive than it already was by encrusting one in crystals. In
fact, it might have been that that finally made Samsung, or its retailers, see
sense as prices of the gadget, sans bling, were slashed to below ?500 for the
first time.

Not quite on the shelves but soon ...

1/18/2011 3:09:00 AM

...Now looking for people to sell it

There's nothing quite like Memjet's colour printing technology when it's going
at full pelt. Almost as soon as the paper has entered the machine, it is
coughed out the other end, resplendent with colour pictures and graphics. And
the pages are dry to the touch almost instantly too. Clearly pixie magic is at
work...

Well, not quite. After all, you try rounding up five pixies, one for each
colour, and bribing them to sit inside plastic shell day and night. It's not
easy, for starters, there's the unions to worry about.

Instead, Memjet uses more than 70,000 ink nozzles on a single printhead, 17
times that of conventional inkjet printers. Plus, its printhead is?222.8mm
wide, spanning the width of an A4 page, so it doesn't need to whizz back and
forth like with many of its peers and rivals. The end result is that the
Memjet technology can deliver more than 700 million drops of ink per second
onto a page.

Therefore, a Memjet powered printer can print 60 full colour, 1600 x 800 dpi
pages a minute, one per second. It's like watching the beginning of any movie
that ...

Busy, busy, busy

One often looks at CES and January as the biggest moments in the tech calendar
but there's no doubt that 2010 was all about September. The month started with
a bang as this year's IFA show in Berlin caught the beginning of autumn rather
than the end of August as it sometimes does. With the iPad launch earlier in
2010, we were all expecting a year of tablets and we weren't disappointed.
Finally, the world met the Android powered, 7-inch Samsung Galaxy Tab and
there was even a little competition with the Toshiba Folio 100 as well. Aside
those treats, it was the usual case of a world of AV products - 3D being the
watchword - as well as a promise from Motorola that we'd see a tablet from
them come CES 2011. Watch this space.

For the gritty details of everything that whent down in Berlin, take a look at
our IFA 2010 homepage but, if it was the tablets you're after, then it was
elsewhere we got a glimpse - albeit behind glass - of other gadgets in this
emerging space. September also saw BlackBerry's annual event in ...

12 reasons why, this is the gift to buy

Forget the calling birds, the 4th day of Christmas is about something else
entirely in the modern world and we're about to tell you exactly what that is.
In case you're not up to speed, welcome to the 12 days of Christmas on Pocket-
lint where we give you solid gold advice on what to stick under the tree for
your loved ones this year. Frankincense and myrrh not included.

Today's giftoid is on the surface not so exciting but we've got 12 watertight
reasons why that just simply ain't so. So, get you Christmas list open, your
credit it card out and prepare to have a problem solved.

?

### Kodak ESP 5250 all-in-one printer

What is it?

Photo printer and more

Who's it for?

Parent/grandparent

How much is it?

?99

Delivery speed?

2 days

**It's easy to set up and use**

This is Kodak and there's a family heritage here to protect and work with, so
you can bet that setting up the ESP 5250 is going to be as straight forward as
installing a printer gets. Naturally, it's all pretty clearly marked with
manuals and a wizard. What's more, the paper tray has an intelligent sensor
which detects what source material you've put in, meaning that there's no need
know anything about the settings to get it right. It's as idiot proof as they
come.

**You don't need to plug it in**

Better still, you don't even need to plug the thing in. Well, you do but only
to the wall and just about anyone can manage that part of things. Beyond that,
the printer works over Wi-Fi, so your giftee doesn't need to do any getting
behind the back of the computer to be faced with a series of scary ports and
down the barrel of confusion. It also means no having to get on your hands and
knees which might be a help for those with back problems.

**It's cheap to run**

The Kodak printers aren't just cheap to run, the industry has named them the
cheapest. The decent outlay that you'll have made on your loved one's behalf
ensures that they get one of the most ink efficient machines out there. So
your giftee won't end up spending more on cartrdiges in the first year than
you did on the printer to begin with.

**There's only two kinds of cartridge**

Running low on ink is the bane of the photo printer's life and the really good
news here is that the ESP 5520 only takes two cartridges - black and colour.
So, the person you give this to is not going to have to deal with warnings
every three minutes about how they're running low on cyan or trying to work
out just what colour K is anyway.

**You get Kodak lab-quality photos**

If you use Kodak photo paper, Kodak ink cartrdiges and print with the Kodak
software installed, then you're guaranteed to get photo print outs as good as
the ones you used to get from your high street Kodak labs. In other words,
they're really good.

**Your prints will last you over 100 years**

The combination of pigment inks and swellable papers in the Kodak printing
system means that not only are the colours going to be top notch but the
images will last for over 100 years. Take a look at a Polaroid shot you took
when you were young and the state of it now and you'll know what we mean.

**It's under ?100**

Self-explanatory really. It, as in the printer, is under, like the opposite of
over and also meaning beneath, 100, first of the three figure integers,
pounds, unit of currency in the United Kingdom. What that also means is that,
so far, the Kodak ESP 5250 is the cheapest gift in the Pocket-int 12 Days of
Christmas.

**It looks really big under the tree**

They say that size isn't everything but that's just not true when it comes to
Christmas presents. Everyone wants that big one under the tree to be theirs
and, if you get this for somebody, you've already scored points before its
even been opened.

**It's a copier and scanner as well**

This is an all-in-one printer, as it goes. So, it's not just photo and paper
printing that it'll do. Should your giftee be up to the task, they'll be able
to scan documents and use the 5250 as a photocopier too.

**It's as non-threatening as you're going to get**

Kodak might not conjure up the phrase high tech but it does inspire trust. If
you're buying for someone not entirely comfortable with the new-fangled age,
then the best shot you can offer them is a brand they understand in the first
place. No promises that your gran will be scanning her shopping lists but
this'll be your best bet.

**You can print without a computer**

As with many modern printers, the Kodak ESP 5250 has an SD card slot so that
you can print direct from your memory stick without having to switch on the
computer at all. Rather useful if your giftee isn't particularly PC literate.
If, however, they're a bit of a gadget fiend, it's also a good buy as there's
an iPhone/iPod app that you can your mobile snaps from as well.

**It's energy efficient**

As if all that isn't enough, the Kodak ESP 5250 is Energy Star qualified and
what that boils down to is that it runs in standby at less than 1W. So, if you
forget to turn it off, it's not going to destroy the rainforests - a sapling
perhaps, but that's about it.

FULL REVIEW

Related links:

* Day 1 - 12 Days of Christmas: Amazon Kindle 3G + Wi-Fi

* Day 2 - 12 Days of Christmas: Xbox 360 S

* Day 3 - 12 Days of Christmas: BlackBerry Curve 8520 Pink

* Feature - Why is printing so bloody expensive?

* Feature - How to buy the right printer for you

Tags: Printers 12 Days of Christmas Features Christmas Kodak ESP 5250

12 Days of Christmas - Kodak ESP 5250 Printer originally appeared on
http://www.pocket-lint.com on Sat, 04 Dec 2010 12:30:00 +0000

Poor timing though just as AirPrint goes live

If you're gonna announce to the world that you've developed the "world's
first" iPhone printer - it's probably best not to do it on exactly the same
day that Apple goes live with iOS 4.2, and the AirPrint function.

But that is what Bolle has done with its device - the Bolle Photo.

Oh well. Poor timing aside, this is quite a nifty looking little device that
docks your iPhone, charges it, and gives you a few printing options for its 6
x 4-inch (A6) output.

Using the accompanying free app, you can choose single pics to print off, or
you can select multiple images - and there's even a passport photo printing
option.

That's about it really, but at ?119.99, you might find it useful.

The Bolle BP-10 Photo printer is available now at MobileFun.

?

Tags: iPhone docks iPod docks Bolle Photo Printers

Bolle unveils "world's first" iPhone printer originally appeared on http://www
.pocket-lint.com on Mon, 22 Nov 2010 15:55:00 +0000

10 questions you're going to need an answer for

You are the techno-gadget person in your family. There's no two ways about it.
You definitely are. That's why you're here at Pocket-lint in the first place.
So as the expert, naturally you're going to be the first port of call for any
IT problem, any device suggestion and any new-fangled term your loved ones
have picked up at all in 2010.

It can be a pretty tedious affair having to explain some of this stuff to
people that just don't get it. Fortunately, as ever, we're here to help save
the day. Here are a list of the 10 questions you're most likely to be asked
and the simplest ways of dealing with them.

### What is Facebook Places?

This is a tricky one because you're essentially going to be dealing with two
questions here. The first is about explaining what it is and the second is
going to be a quick follow up on why anyone would want to use it. So, the best
tactic here is to deal with both of them at once. All you need to do to keep
it short ...

Feedzilla.

10 ways to impress your family with the gadget knowledge that you don't even
have

Christmas is a time for giving and sharing. It's also a time for total
confusion for the non-tech savvy. Each and every time they get another year
older and another whole 12 months further adrift of what the world of
technology is up to. Christmas Day is the sad reminder of that fact, as
wrapping paper goes flying and yet another incomprehensible gadget comes out
of a box to oohs and ahhs of everyone else but to the total bewilderment of
others.

We at Pocket-lint believe that technology is for all and have decided that it
is our duty this time around to bring those less connected back into the fold
and make sure that no conversation is too daunting a task. So, here are 10
ways you can bluff gadget knowledge to your Christmas guests, friends and
relatives. We guarantee you'll learn a little something and it'll be worth it
to watch your loved ones fall off their perches in shock. Remember, the more
lingo, the better.

### Offer the Wi-Fi code when they walk through the door

You probably have ...

If you've got a huge amount of photos you'd like to scan, it's often faster
and easier to trust someone else to do it--otherwise, scanning photos one at a
time can be a very time-consuming process. But it's not easy to compare these
services, since they all have lots of different deals and requirements. This
comparison chart of online photo-scanning services should help you compare
pricing between some of the biggest players.

Which is faster? One lap around Rockingham to find out

Epson claims that its Stylus Office range of printers are some of the fastest
on the planet, being able to cough out 38 black and white or colour prints a
minute. But that could just be bold hyperbole.

So, to prove their uncanny ability to go through sheets faster than
the?dysentery?ward at University College Hospital, the Japanese company came
up with the sort of madcap scheme normally reserved for Top Gear.

Indeed, it hired one of Top Gear's director,?Phil Churchward, to put together
a video of one of the most bizarre races ever run; an Epson Stylus Office
printer versus a customised Ariel Atom racing car.

The car was customised to house the printer itself, and the idea was to race
one lap of Rockingham racetrack in Corby, Northamptonshire. However, while the
car would perform one entire circuit, the printer would have to print it via
Wi-Fi.

It proved just as crazy as it sounds and, at one point, quite dangerous for
the driver. But, for the ending and result, you'll just have to watch the vid
for yourself.

Tags: Laptops Printers Epson Epson Stylus Office BX610FW Ariel Atom

VIDEO: Epson Stylus Office printer vs Ariel Atom racing car originally
appeared on http://www.pocket-lint.com on Thu, 11 Nov 2010 15:42:27 +0000

20,000 Custom Printed Jumbo Mailer Postcards, 6 x 11, Premium Cards, Double Sided, High Resolution

pc news

2011-03-08T01:40:00.000-08:00

Pcs News

If you thought 3-D was a tough sell for the living room, now imagine if you
had to lug the technology around with you. That, in fact, is the big sell of
the HP Envy 17 3D, and any other 3-D-equipped laptop: it gives you the world
of three dimensions on the go. Can you feel the excitement? No? Well, ahem.

Taiwanese computer manufacturer Acer has announced plans to release both a
7-inch and a 10-inch tablet in 2011. These Android-powered devices will
eventually replace the company's netbooks, sales of which are dwindling.

We recently got a closer look at two tablets shown off in Microsoft CEO Steve
Ballmer's CES 2011 keynote: The Acer Iconia and the Asus Eee Slate EP121.
Together, they show the potential -- and the limitations -- of a Windows-based
tablet strategy.

After months of speculation, HP appears ready to release its new PalmPad
tablet PC at the Consumer Electronics Show in two weeks, according to one
report.

Word on the street is that Microsoft plans to announce a Windows-powered iPad
contender at next month’s Consumer Electronics Show. Here are seven reasons
buying a Windows 7 slate would be a bad idea.

In what very much appears to be a controlled leak from Microsoft, _The New
York Times_ has detailed "rumors" of upcoming Windows "slates" that will be
shown off by Steve Ballmer at CES next month.

Google's Cr-48 netbook is a promising but incomplete step toward a life lived
fully on the internet.

Get a quick summary of details about Chrome OS, Google's new browser-based
operating system, set to ship on netbooks in 2011.

Samsung's Galaxy Tab, a 7-inch tablet powered by the Android operating system,
has made its rounds with gadget reviewers, and consensus says it's a solid but
pricey device.

Apple is on a mission to cram the iPad's successes into the Mac, beginning
with a brand-new App Store serving Mac software. That can be both good and
bad, according to programmers.

Apple has rolled out major upgrades for its puny MacBook Air -- the machine
that Steve Jobs believes is the "future of notebooks." Wired.com had some
hands-on time with the Air, which now comes in 13.3-inch and 11.6-inch models.
Follow along for our impressions and photos of the devices.

10/19/2010 10:50:00 AM

Here’s a quick rundown of what Apple is likely to unveil at Wednesday's "Back
to the Mac" news conference.

If you count iPads as computers, Apple could now be said to have the largest
market share of any computer maker in the United States.

Sha

pc

2011-03-08T01:23:00.000-08:00

Pc News

Sh via Feedzilla.

After months of speculation, HP appears ready to release its new PalmPad
tablet PC at the Consumer Electronics Show in two weeks, according to one
report.

In what very much appears to be a controlled leak from Microsoft, _The New
York Times_ has detailed "rumors" of upcoming Windows "slates" that will be
shown off by Steve Ballmer at CES next month.

Google's Cr-48 netbook is a promising but incomplete step toward a life lived
fully on the internet.

Get a quick summary of details about Chrome OS, Google's new browser-based
operating system, set to ship on netbooks in 2011.

Samsung's Galaxy Tab, a 7-inch tablet powered by the Android operating system,
has made its rounds with gadget reviewers, and consensus says it's a solid but
pricey device.

Apple is on a mission to cram the iPad's successes into the Mac, beginning
with a brand-new App Store serving Mac software. That can be both good and
bad, according to programmers.

10/19/2010 10:50:00 AM

Here’s a quick rundown of what Apple is likely to unveil at Wednesday's "Back
to the Mac" news conference.

If you count iPads as computers, Apple could now be said to have the largest
market share of any computer maker in the United States.

Sha

Laptops

2011-03-08T01:00:00.000-08:00

Laptops - Reviews

Apple is unveiling its iPad 2 at an event next Wednesday, but what else will
it announce? Reports suggest iOS 4.3 may be released into the wild, while
Apple's MobileMe service may get relaunched.

Apple has shown off a preview of Lion, the next version of the Mac OS X, and

Apple's new MacBook Pro range shows off a brand-new, super-speedy method of
connecting your laptop to other devices: Thunderbolt.

Apple will unveil its iPad 2 next Wednesday at an event in San Francisco, as
was made clear by yesterday's official invite to journalists. The announcement
has intensified the speculation about the device.

Looking forward to getting your hands on HTC's Flyer tablet? So are we. It
looks like a Wi-Fi-only version of the Android slate will be on the way to the
UK sooner rather than later.

Amazon may be plotting a way around Apple's new rules on subscriptions and in-
app purchases for iPhone, iPod touch and iPad users, involving a mobile web
Kindle e-reader service.

The price is right and the screen is ample, but the experience is outdated and
performance is sluggish.

Apple has issued invitations to what looks like the launch of the second iPad
-- and you're invited too. There's an event in London, which usually means
it'll be out very soon...

Google has greenlighted Android apps for tablets with the release of the final
Honeycomb software development kit.

While the Toshiba Satellite C655-S5130 cracks the $400 barrier for an
affordable 15-inch laptop, this particular AMD Fusion-powered laptop
underperforms and underdelivers.

We've rounded up the rumours, speculation and bare-faced flim-flammery
surrounding the next Apple iPad. What can you expect from the iPad 2?

Sony ditches the Netbook for this more upscale AMD-powered ultraportable, with
good performance and features, but also an upscale price.

Despite reports of a potential delay for the iPad 2, Apple is expected to hold
an event on 2 March to unveil its new tablet. Other speculation, though,
points to a possible iPhone 5 delay.

Sony's unveiled a new line of mid-range laptops, the C series, in a range of
eye-popping colours. Don your sunglasses and click through our hands-on photos
to check 'em out.

If you're looking for a budget-level Netbook with a long battery life, the HP
Mini 1103 offers a very affordable package compared with other HP Netbooks.
Just be forewarned: there isn't anything here you haven't seen before.

Adobe has confirmed rumours that the Motorola Xoom tablet will ship without
Flash, but it's also promised that its software will be available within weeks
of the device's launch.

Share With Frien

The Asus U41JF is a workmanlike but uninspiring 14-inch laptop that offers
decent performance and graphics and excellent battery life, but costs nearly
as much as a MacBook.

audio

2011-03-08T00:21:00.000-08:00

Audio

Cans that go up to 11?

Nowadays, headphones aren't just a way of listening to your music without
annoying people on the bus, they're also a fashion accessory. We've had plenty
of cool-looking headphones on the the Pocket-lint test bench including Philips
O'Neill The Stretch cans and Sennheiser Adidas HD 25-1-II. While both of these
headphones got good scores, there is a danger of style taking over from
substance. The latest traditionally non-headphone brand to get its name on a
pair of cans is legendary guitar amp manufacturer Marshall. But, is the
product any good? Read on to find out.

There's no mistaking that the familiar design boasted by the Marshall Major
headphones is based on the aesthetics from the brand's amps. The telltale
white Marshall logo is proudly displayed on the centre of each earcup and it's
also etched into two metal plates found in the inside of each end of the
headband. Also on the inside of the headband, in the centre you'll find the
signature of company founder Jim Marshall. The outside of the earcups features
a textured finish that feels similar (though not identical) to the vinyl that
the

Tunes on the go

Pocket-Lint has teamed up with audio specialist, Memorex, to give four lucky
readers the chance to win a PurePlay iPod docking station worth ?50.

The PurePlay sound system is a compact, clutch-style device designed to be
easily portable. Its folding design means the speakers are protected while
you're on the move, so you can easily take it down to the beach, on a picnic,
or just play your favourite music indoors, all while charging your iPod or
iPhone.

?

At Pocket-Lint we recently reviewed the PurePlay sound system, awarding it an
impressive 4 out of 5 stars. For more information, make sure you check out our
review here.

And to be in with a chance of winning, just click through here to the
competition page.

Tags: Audio Memorex Memorex PurePlay Competitions

Win 1 of 4 Memorex PurePlay sound systems originally appeared on http://www
.pocket-lint.com on Thu, 03 Mar 2011 11:31:28 +0000

Cool cans that won't break the bank

At the recent Bristol Sound & Vision Show, we spied these cool-looking
headphones from Hong Kong-based manufacturer i-Mego, so we zeroed in on them
for a closer look. Already selling in the US, and on their way to the UK soon,
the Retro range comprises three models - Classics, Heavy and Infinity.

All three models feature the same retro-styling, with the chrome finished cans
looking very similar to a old-style microphones. The earcups themselves have
plenty of padding along with a slightly strange square shape, which we found
to be really comfortable to wear. The earcups also feature a tiny red, fabric
i-Mego label that doesn't look too dissimilar to the labels found on Levi's
jeans for a bit of extra 1950s cool.

The entry-level Classics feature a white and silver finish and are intended
for any type of music, while the step-up Heavy cans sport an unusual deep
brown and smoky chrome look and have enhanced bass response, making them a
good bet for bass-laden dance or rocks tracks. The top-of-the-range Infinity
headphones feature an all-leather black trim as well as the the same bass
technology found on ...

New cans and buds announced

Sony has announced a number of new headphones and earphones, ranging from
professional quality cans down to mobile friendly buds.

Starting with the big boy of the launch bunch, the MDR-Z1000 is designed for
the studio and packs ultra-wide range HD driver units that use a newly-
developed Liquid Crystal Polymer diaphragm, resulting in a light-weight but
sturdy disposition.

These headphones have noise isolation earpads and the cord is made of 7N
Grade, 99.99999 per cent, oxygen free copper. The frequency response is
5-80,000Hz and the sensitivity is 108dB/mW.

Next up is the MRR-ZX series, comprising of the flagship ZX700 as well as the
ZX500, ZX300 and ZX100.

These are headphones with your MP3 player in mind, and feature a closed design
to keep your sound to yourself, so you won't annoy fellow commuters or co-
workers by leaking Coldplay to their poor eardrums.

If you're more earphone friendly then the in-ear MDR-EX series (seven models
in total) may be more up your street.

The best of the EX bunch is the MDR-EX1000 which features a Liquid Crystal
Polymer (LCP) film diaphragm and a 16mm driver unit in a slim magnesium, and
uses the ...

Gets ?18.5million windfall, mind

Apple design guru Jonathan "Jony" Ive is to move back to his Somerset home in
the UK and commute to Cupertino, California when needed, reports state. And,
naturally, this would take him out of the running to take over from Steve Jobs
as CEO if the big man steps down permanently due to health issues.

It is said that Ive and his wife have long wanted their children to be
educated in England, being parents of twin boys, but Apple is understandably
at "loggerheads" with his decision to relocate. It could even cost him his
current senior position within the company.

The Times spoke to an unnamed friend of his: "Unfortunately he is just too
valuable to Apple and they told him in no uncertain terms that if he headed
back to England he would not be able to sustain his position with them."

However, it's unlikely that Apple would be willing to?jettison?the chief
designer of such products as the iPod, iPhone and iPad.

That said, it's not like he needs the money. A recent share option windfall
has just awarded Ive an extra ?18.5million ($30million), should he decide to
sell up. ...

All-in-one, high-end streaming

High-end audio specialist Cyrus has introduced a new range of streaming
products including the all-in-one Streamline. We went along to the Bristol-
based Sound & Vision Show 2011 to get a closer look.

There are three models to choose from in the range, but priced at ?1,600, the
Streamline is the most affordable by far, although you will need to shell out
extra for some loudspeakers to go with it. Based on the same platform as the
flagship Stream XP, the unit itself is very compact and the brushed metal
finish gives it a premium look. Equipped with a 2 x 30W power amp, the
Streamline has everything you need to stream music wirelessly around your home
from a NAS drive (with the addition of some speakers, of course). If the
built-in power amp doesn't offer enough juice for you then the product offers
the flexibility of adding more powerful amps.

As well as looking slick, the Streamline is very easy to use and also has a
USB port so that you can hook up an iPod or portable storage device. There's
also an Ethernet port in case you prefer a wired ...

Morning glory

There are some things, in Britain anyway, that are absolute musts if you're
going to get through the day, without getting extremely angry with the world.

There are three that spring to mind straight away: toast, tea and a bit of
morning radio. Something that the Breville radio toaster has a really good go
at taking care of, and anyway two out of three ain't bad.

Lack of a good cup of tea aside and this gadget has it all, as you not only
get to listen to your favourite radio station, but there is the built-in
toaster as well. Both FM and AM bands are taken care of and there's also a
variable browning function and mid-cycle cancel tech on board.

10 preset radio channels and removable crumb tray for easy clean, rounds off
the package and if you're still not convinced, blue illuminated toasting
controls come as standard - yes, standard.

Priced at ?49.99 from Firebox.com you'd have thought Breville would have
fitted some kind of tea-making functionality, but it's still something you'd
be proud of sitting on the counter of your kitchen.

?

Read

Tags: Audio Radios Breville Gadgets Toasters Home And Kitchen ...

After UK d?but

Two months after Sony launched its Qriocity powered music-on-demand platform
in the UK and Europe, it has announced the arrival of Music Unlimited powered
by Qriocity in the US (and Australia and New Zealand too).?

The subscription-based package will give its users access to tonnes of songs
from many of the major record labels including Universal Music Group, Sony
Music Entertainment, Warner Music Group and EMI Music as well as some of the
leading independent labels.?

You can access and play tunes through a range of Sony devices including the
2010 Bravia TVs, Blu-ray players and home theatre systems, as well as
PlayStation 3 consoles and Vaio PCs.

There's also plans afoot to bring the service to Android devices and "a wide
range of Sony's portable devices" - could this be the Sony Qriocity tablet we
told you about on Wednesday?

"As we expand 'Music Unlimited powered by Qriocity' around the globe, it
signifies a paradigm shift which redefines the existing music listening
experience by revolutionising music access, discovery, integration and
personalisation," said Kazuo Hirai, president of Networked Products & Services
Group, Sony Corporation.

"Through Sony's high quality network-enabled devices, we are focused on
delivering dynamic services ...

MWC 2011: We listen in on new app

Sonos?fans that just happen to be rocking Android we've got some bad news -
we've played with the new Android Sonos app and you haven't.

That's right, we've tracked down the chaps at Sonos at Mobile World
Congress?in Barcelona and had a quick play with the new Android app and a
Sonos S5.

It's at this point we have to admit we planned to have a longer play than we
did, but with so many Wi-Fi networks on the Google stand we're surprised the
Sonos guys managed to keep connectivity as long as they did.?Hats off guys.

Anyway, back in the real world where there aren't five dozen Wi-Fi networks
and about 300 mobile phones vying for connectivity, and the app is likely to
work perfectly.

For iPhone users who are looking for the excuse to jump ship to an Android
device the concept is the same. In fact if it wasn't for the slightly
different blue tint on the interface (it's more turquoise - random we know)
you would be hard pushed to tell the difference between the two when it comes
to the User Interface (UI).

Of ...

Facebook and Twitter campaign used

Radiohead used the power of the web and its social networks to announce the
arrival of their new album "The Kings Of Limbs", which once again bypasses the
major record labels.

The news first broke on the band's website, with a post simply saying "Thank
You for waiting", and the album's pre-order status was declared by the
Radiohead News Facebook page, as well as its Twitter account, so the fans knew
about the launch even before the music press did.

The Kings of Limbs is available to pre-order now at ateaseweb.com. It will go
on general release on both CD and 12-inch vinyl in all music stores and
digital retailers from 28 March.

Nigel Godrich, who has worked with the band from 1997's OK Computer onwards,
is again on board to produce the album.

Let's just hope it's more The Bends than In Rainbows.

Read

Tags: Digital music Radiohead Audio Music Social networks

Radiohead use the social network for new album launch originally appeared on
http://www.pocket-lint.com on Mon, 14 Feb 2011 13:58:00 +0000

Street-style cans for wannabe DJs

With the number of amateur DJs increasing by the day, plenty of audio brands
are now offering fashionable headphones with rotating earpieces for the one-
eared listening position that's a prerequisite of the DJ stance.

Clearly targeted at the young hipster market, Panasonic's RP-DJS400 DJ
headphones have been designed as a fashion statement and are available in a
choice of three colourways - white with green accents, black with orange and
orange with grey. The idea is that they look just as cool when they're hung
around your neck as when you're wearing them. We're not entirely sure if
that's what really counts as being cool these days, but we're happy to play
along for the benefit of our review. And in fairness, the vivid combination of
white and green on our review sample really does look pretty snappy.

On closer inspection, the glossy white plastic finish on the earcups looks a
little cheap but we can't really complain too much as the headphones only cost
?40.99. Both earcups can be swiveled around by 90 degrees so that they fold
flat and can also be used for DJ-style, one-sided listening. ...

We go jogging with these sporty buds

One member of team Pocket-lint is quite the athletic type. He laughs in the
face of triathlons and knocks-out marathon-length jogs on Sunday mornings for
fun.

Unfortunately, this writer is not that team-member and is instead a rather
lazy individual who really should get his act together. But still, we're often
running around the corner to the pub in order to get in before last orders, or
running away from crazed landlords after arguing that it's 10.59, not 11.03 as
the pub's clock says.

So we think we're more than qualified to take the sporty Radiopaq Flex
earphones for a test-run. We were perfectly able to see if they would fit
nicely, or if they'd stay in place when we ran up to the shops - yes, and yes
by the way.

These budget sporty buds (less than ?25) may not be the best quality earphones
you're likely to come across (and you'd get better quality for the same money
from the likes of Sennheiser) but they do exactly what they state on the tin -
they hook to your ears and they stay in place when you're moving ...

itllicius

2011-03-05T23:35:00.000-08:00

WEB CREATION

3/3/2011 8:52:00 PM

Voice Extensible Markup Language or voiceXML is the file format used by a
voice browser. To understand more about VXML, you must learn a few related
terms. Learn more about VXML and how to get your XML heard in this article by
Darla Ferrara.

**Read the full article:** XML and Voice-Web Applications - What is VXML

You can Write XML to Be Heard, Not Read originally appeared on About.com Web
Design / HTML on Friday, March 4th, 2011 at 04:51:30.

Permalink | Comment | Email this

Share With Friends: | | Lybia Protests News, Internet - Web Development News, News Feeds and News via Feedzilla.

3/3/2011 9:45:00 AM

The recent highly publicized piece in Vogue magazine describes you as a
humanitarian with a passion for children's issues, among other things. Like
you and Mr. President Bashar al-Assad, loving parents of your son, little
Hafez al-Assad, I do not wish to see my precious daughter Sofia in one of the
orphanages you often visit in your country. I await your response and hope the
Syrian Government will take urgent action to assist the United States Embassy
in Damascus in their search for my daughter and with her safe return home. I
thank you in advance for your prompt response.

read more

Share With Friends: | | Lybia Protests News, Internet - Web Development Stories, RSS Feeds and Widgets via Feedzilla.

3/2/2011 8:31:00 PM

There are so many high quality WYSIWYG editors out there that many beginning
web designers don't see any need to learn the back end languages of HTML, CSS,
JavaScript, or PHP. But is that wise? Do you think it's important for
designers to know how to write HTML? What languages should designers learn?

Poll: Should designers know how to code? originally appeared on About.com Web
Design / HTML on Thursday, March 3rd, 2011 at 04:31:13.

Permalink | Comment | Email this

Share With Friends: | | Lybia Protests News, Internet - Web Development News, RSS Feeds and Widgets via Feedzilla.

3/2/2011 9:30:00 AM

The possibility of embedding any font you like into websites via `@font-face`
is an additional stylistic device which promises to abolish the monotony of
the usual system fonts. It surely would be all too easy if there was only one
Web font format out there. Instead, there's quite a variety, as you will get
to know in this article.

This quick introduction to `@font-face` will lead you towards a guide through
the `@font-face` kit generator. If you want to make Web use of your already
licensed desktop fonts, read up on how to embed them from your own server.
Topped up with some helpful tips, tricks and workarounds, this article will
hopefully provide some useful insights.

Share With Friends: | | Lybia Protests News, Internet - Web Development News, News Feeds and News via Feedzilla.

3/1/2011 8:46:00 PM

Get the site you're working on featured on About.com: What's in Your Editor?

More Web design resources and help: Follow me on Twitter or Become a Fan on
Facebook

Wordless Wednesday: What's In Your Editor - Lunsford Illustration originally
appeared on About.com Web Design / HTML on Wednesday, March 2nd, 2011 at
04:46:07.

Permalink | Comment | Email this

Share With Friends: | | Lybia Protests News, Internet - Web Development Stories, RSS Feeds and Widgets via Feedzilla.

3/1/2011 10:18:00 AM

House Republicans' war against net neutrality rules is symptomatic of a gross
simplification of economic principles that is typical of today's Tea-flavored
Republican party.

Share With Friends: | | Lybia Protests News, Internet - Web Development News, RSS and RSS Feed via Feedzilla.

3/1/2011 7:58:00 AM

Those of you who saw my talks at either Future of Web Design in NYC, or at
Webstock in Wellington may remember a segment where I urged delivering value
as quickly as possible. In that segment, I compared the act of taking and
sharing a photo with Hipstamatic, and the same in Instagram. I posited [...]

Share With Friends: | | Lybia Protests News, Internet - Web Development News, RSS and RSS Feed via Feedzilla.

2/23/2011 5:43:00 AM

MY DAUGHTER sat laughing in the dark, her face and hands covered in blood.
Just a nosebleed but it aged me 10 years.

Share With Friends: | | Lybia Protests News, Internet - Web Development News, News Feeds and News via Feedzilla.

2/27/2011 12:00:00 PM

Scality, a French cloud storage start-up-gone-Californian, picked up a $7
million B round Tuesday led by IdInvest Partners (née AGF Private Equity).
It’s going to spend the money on a sales and services office in New York and
enhancements to its distributed object-based storage platform, adding full
multi-tenancy for Service Providers that want to offer virtual private clouds,
and a new tiering algorithm for private clouds environments. Total investment
in Scality to date is $13 million. It says its valuation doubled after its A
round last May 2010 thanks to the successful delivery of a complete e-mail
platform to cable operator Telenet for over two million users and the very
strong sales pipeline.

read more

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2/7/2011 4:45:00 AM

IBM is putting a $42 million cloud computing data center in Canada. It’s
supposed to meet Canadian privacy rules. The market is estimated to grow by
40% over the next three years according to IDC. Meanwhile, HP is going to
build a data center in Georgia in the Caucasus that will provide IT services
to the Georgian government and clients in Eastern Europe and parts of the old
Soviet Union.

read more

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2/28/2011 11:40:00 PM

Compatibility view is a new feature in IE 8 that allows this browser to change
how it renders web pages to emulate previous, less standards compliant
versions of the browser. And you may have customers who have set up IE to
display all web pages in compatibility view rather than standards view, which
can affect how your pages will look.

**Read the full article:** What is Internet Explorer Compatibility View?

###

* How to Force Internet Explorer to View a Page in Compatibility Mode (or
Not)

* Designing Web Pages with Internet Explorer

* Microsoft Internet Explorer

If you Design Pages for IE 8 You Should Know About Compatibility View
originally appeared on About.com Web Design / HTML on Tuesday, March 1st, 2011
at 07:39:44.

Permalink | Comment | Email this

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3/1/2011 7:20:00 AM

As most of you may already know, every second Tuesday of a month we send out
an email newsletter to our subscribers (over 50,000 at the moment). Every
newsletter issue contains exclusive, short articles that present recent design
techniques, freebies as well as useful resources and tools. We work hard to
make every issue special and useful, interesting and entertaining, and
therefore your feedback is very important to us. (Feel free to take a look at
the latest newsletter issue).

Today, we’re particularly pleased to announce that our Smashing Newsletter is
turning one year old tomorrow (yaaaaay!). To celebrate this special day, we'd
like to **give away some remarkable, must-have books**. Besides, we'd like to
look back at the last year and present you a selection of the most interesting
articles from our previous issues. And, just for the record, the next issue is
coming up tomorrow.

The Smashing Newsletter has always been free of charge. We fully respect your
privacy, and we would never share your data with third parties, nor would we
ever spam you. You have our word.

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2/28/2011 6:11:00 AM

We always try our best to challenge your artistic abilities and produce some
interesting, beautiful and creative artwork. And as designers we usually turn
to different sources of inspiration. As a matter of fact, we’ve discovered the
best one -- desktop wallpapers that are a little more distinctive than the
usual crowd. This creativity mission has been going on for almost two years
now, and we are very thankful to all designers who have contributed and are
still diligently contributing each month.

We continue to nourish you with a monthly spoon of inspiration for the next 12
months. This post features **35 free desktop wallpapers** created by artists
across the globe for March 2011. Both versions with a calendar and without a
calendar can be downloaded for free. It’s time to freshen up your wallpaper!

Please note that:

* All **images can be clicked on** and lead to the preview of the wallpaper,

* You can feature your work in our magazine by taking part in our Desktop
Wallpaper Calendar series. We are regularly looking for creative designers and
artists to be featured on Smashing Magazine. Are you one of them?

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2/22/2011 8:34:00 AM

In Issue No. 324 of A List Apart, for people who make websites: Web
Cryptography: Salted Hash and Other Tasty Dishes by LYLE MULLICAN One of the
most powerful security tools available to web developers is
cryptography—essentially a process by which meaningful information is turned
into random noise, unreadable except where specifically intended. A web [...]

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2/27/2011 11:02:00 AM

Sometimes I become a bit skeptical when I see the huge uptake in social media
by B2B marketers. In fact, recent research by Junta42 and Marketing Profs
finds that use of social media is the top B2B tactic in use as identified by
79% of 985 marketers. Unfortunately, only 31% of those marketers said they
found it effective. In a recent Harvard Business Review Analytic Services
study, only 12% of 2,100 executives say that their companies are using social
media effectively. So what's the biggest question to ask when using B2B social
media in marketing?

read more

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2/27/2011 11:36:00 PM

I do my work on a Macintosh computer, but I have two virtual machines running
Windows on it so that I can do testing and evaluation of web designs in
Internet Explorer. IE may not have the majority share of the browser market,
but it still has the largest share (around 40-45% in January 2011). And so if
I ignore it, I am not doing my sites or my customers any favors. Learn more
about this browser and how to use it to design web pages in my latest article.

**Read the full article:** Designing Web Pages with Internet Explorer

### IE Specific Tricks

* What Web Browser Do You Use?

* Enable HTML 5 in Internet Explorer

* Comments in Microsoft Internet Explorer

* Quick Fix to the Q Tag in IE

Internet Explorer is an Important Part of Web Design Work originally appeared
on About.com Web Design / HTML on Monday, February 28th, 2011 at 07:36:20.

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2/22/2011 8:30:00 AM

Enjoy Kafka For Lovers.

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2/27/2011 10:15:00 AM

Queplix Wednesday put a couple of tools on the market that are supposed to
make it easier, quicker and cheaper to move data to the cloud. Its new
VirtualETL and CloudETL lines bring data virtualization to usually thorny
extract, transform and load (ETL) tasks and are supposed to cut the time
required to connect applications a good 75% compared to traditional ETL
methodologies. Queplix CEO Mark Cashman says using data virtualization for ETL
“changes everything; ETL teams can mix any combination of relational, object,
cloud or XML-based applications. And they don’t need to use SQL to set up
connectivity, define the transforms, tune data quality or get the integration
into production. We’ve essentially turned the cost model upside down, lowering
product costs and dramatically reducing set-up costs.”

read more

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best perfomers

2011-02-25T00:32:00.000-08:00

WORK AT HOME

2011-01-13T23:51:00.000-08:00

I REALLY THINK ITS IMPOSSIBLE I HAVE TRIED MY BEST BUT ALL IN VAIN

christmass sales

2010-12-19T22:15:00.000-08:00

TERMINATING

2010-09-13T00:26:00.000-07:00

router

2010-07-26T22:57:00.000-07:00

memory

2010-07-17T01:33:00.000-07:00

POWER SUPPLY

2010-06-23T00:40:00.000-07:00

Computer power supply

Power supplies, often referred to as "switching power supplies", use switcher technology to convert the AC input to lower DC voltages. The typical voltages supplied are:

* 3.3 volts
* 5 volts
* 12 volts

The 3.3- and 5-volts are typically used by digital circuits, while the 12-volt is used to run motors in disk drives and fans. The main specification of a power supply is in watts. A watt is the product of the voltage in volts and the current in amperes or amps. If you have been around PCs for many years, you probably remember that the original PCs had large red toggle switches that had a good bit of heft to them. When you turned the PC on or off, you knew you were doing it. These switches actually controlled the flow of 120 volt power to the power supply.

Today you turn on the power with a little push button, and you turn off the machine with a menu option. These capabilities were added to standard power supplies several years ago. The operating system can send a signal to the power supply to tell it to turn off. The push button sends a 5-volt signal to the power supply to tell it when to turn on. The power supply also has a circuit that supplies 5 volts, called VSB for "standby voltage" even when it is officially "off", so that the button will work. See the next page to lea

===============================================================

Connectors
Various connectors from a computer PSU.

Typically, power supplies have the following connectors:

* PC Main power connector (usually called P1): Is the connector that goes to the motherboard to provide it with power. The connector has 20 or 24 pins. One of the pins belongs to the PS-ON wire (it is usually green). This connector is the largest of all the connectors. In older AT power supplies, this connector was split in two: P8 and P9. A power supply with a 24-pin connector can be used on a motherboard with a 20-pin connector. In cases where the motherboard has a 24-pin connector, some power supplies come with two connectors (one with 20-pin and other with 4-pin) which can be used together to form the 24-pin connector.
* ATX12V 4-pin power connector (also called the P4 power connector). A second connector that goes to the motherboard (in addition to the main 24-pin connector) to supply dedicated power for the processor. For high-end motherboards and processors, more power is required, therefore EPS12V has an 8 pin connector.

* 4-pin Peripheral power connectors (usually called Molex for its manufacturer): These are the other, smaller connectors that go to the various disk drives of the computer. Most of them have four wires: two black, one red, and one yellow. Unlike the standard mains electrical wire color-coding, each black wire is a ground, the red wire is +5 V, and the yellow wire is +12 V. In some cases these are also used to provide additional power to PCI cards such as FireWire 800 cards.
* 4-pin Berg power connectors (usually called Mini-connector or "mini-Molex"): This is one of the smallest connectors that supplies the floppy drive with power. In some cases, it can be used as an auxiliary connector for AGP video cards. Its cable configuration is similar to the Peripheral connector.

* Auxiliary power connectors: There are several types of auxiliary connectors designed to provide additional power if it is needed.
* Serial ATA power connectors: a 15-pin connector for components which use SATA power plugs. This connector supplies power at three different voltages: +3.3, +5, and +12 volts.
* 6-pin Most modern computer power supplies include 6-pin connectors which are generally used for PCI Express graphics cards, but a newly introduced 8-pin connector should be seen on the latest model power supplies. Each PCI Express 6-pin connector can output a maximum of 75 W.
* 6+2 pin For the purpose of backwards compatibility, some connectors designed for use with PCI Express graphics cards feature this kind of pin configuration. It allows either a 6-pin card or an 8-pin card to be connected by using two separate connection modules wired into the same sheath: one with 6 pins and another with 2 pins.
* A C14 IEC connector with an appropriate C13 cord is used to attach the power supply to the local power grid.

Small facts to consider
Redundant power supply.

* Life span is usually measured in mean time between failures (MTBF). Higher MTBF ratings are preferable for longer device life and reliability. Quality construction consisting of industrial grade electrical components and/or a larger or higher speed fan can help to contribute to a higher MTBF rating by keeping critical components cool, thus preventing the unit from overheating. Overheating is a major cause of PSU failure. MTBF value of 100,000 hours is not uncommon.

* Power supplies may have passive or active power factor correction (PFC). Passive PFC is a simple way of increasing the power factor by putting a coil in series with the primary filter capacitors. Active PFC is more complex and can achieve higher PF, up to 99%.

* In computer power supplies that have more than one +12V power rail, it is preferable for stability reasons to spread the power load over the 12V rails evenly to help avoid overloading one of the rails on the power supply.
o Multiple 12V power supply rails are separately current limited as a safety feature; they are not generated separately. Despite widespread belief to the contrary, this separation has no effect on mutual interference between supply rails.
o The ATX12V 2.x and EPS12V power supply standards defer to the IEC 60950 standard, which requires that no more than 240 volt-amps be present between any two accessible points. Thus, each wire must be current-limited to no more than 20 A; typical supplies guarantee 18 A without triggering the current limit. Power supplies capable of delivering more than 18 A at 12 V connect wires in groups to two or more current sensors which will shut down the supply if excess current flows. Unlike a fuse or circuit breaker, these limits reset as soon as the overload is removed.
o Because of the above standards, almost all high-power supplies claim to implement separate rails, however this claim is often false; many omit the necessary current-limit circuitry,[5] both for cost reasons and because it is an irritation to customers.[1] (The lack is sometimes advertised as a feature under names like "rail fusion" or "current sharing".)

* When the computer is powered down but the power supply is still on, it can be started remotely via Wake-on-LAN and Wake-on-Ring or locally via Keyboard Power ON (KBPO) if the motherboard supports it.

* Early PSUs used a conventional (heavy) step-down transformer, but most modern computer power supplies are a type of switched-mode power supply (SMPS) with a ferrite-cored High Frequency transformer.

* Computer power supplies may have short circuit protection, overpower (overload) protection, overvoltage protection, undervoltage protection, overcurrent protection, and over temperature protection.

* Some power supplies come with sleeved cables, which is aesthetically nicer, makes wiring easier and cleaner and have less detrimental effect on airflow.

* There is a popular misconception that a greater power capacity (watt output capacity) is always better. Since supplies are self-certified, a manufacturer's claims may be double or more what is actually provided.[6][7] Although a too-large power supply will have an extra margin of safety as far as not over-loading, a larger unit is often less efficient at lower loads (under 20% of its total capability) and therefore will waste more electricity than a more appropriately sized unit. Additionally, computer power supplies generally do not function properly if they are too lightly loaded. Under no-load conditions they may shut down or malfunction.

* Another popular misconception is that the greater the total watt capacity is, the more suitable the power supply becomes for higher-end graphics cards. The most important factor for judging a PSUs suitability for certain graphics cards is the PSUs total 12V output, as it is that voltage on which modern graphics cards operate. If the total 12V output stated on the PSU is higher than the suggested minimum of the card, then that PSU can fully supply the card. It is however recommended that a PSU should not just cover the graphics cards' demands, as there are other components in the PC that depend on the 12V output, including the CPU and disk drives.

* Power supplies can feature magnetic amplifiers or double-forward converter circuit design.

power

2010-06-14T22:46:00.000-07:00

POWER IS NOTHING WITHOUT CONTROL

eye

2010-05-28T23:58:00.000-07:00

syntax

2010-05-25T23:15:00.000-07:00

syntax
In computer science, the syntax of a programming language is the set of rules that define the combinations of symbols that are considered to be correctly structured programs in that language. The syntax of a language defines its surface form.[1] Text-based programming languages are based on sequences of characters, while visual programming languages are based on the spatial layout and connections between symbols (which may be textual or graphical).

The lexical grammar of a textual language specifies how characters must be chunked into tokens. Other syntax rules specify the permissible sequences of these tokens and the process of assigning meaning to these token sequences is part of semantics.

The syntactic analysis of source code usually entails the transformation of the linear sequence of tokens into a hierarchical syntax tree (abstract syntax trees are one convenient form of syntax tree). This process is called parsing, as it is in syntactic analysis in linguistics. Tools have been written that automatically generate parsers from a specification of a language grammar written in Backus-Naur form, e.g., Yacc (yet another compiler compiler).

Syntax definition
Parse tree of Python code with inset tokenization

The syntax of textual programming languages is usually defined using a combination of regular expressions (for lexical structure) and Backus-Naur Form (for grammatical structure) to inductively specify syntactic categories (non terminals) and terminal symbols. Syntactic categories are defined by rules called productions, which specify the values that belong to a particular syntactic category.[1] Terminal symbols are the concrete characters or strings of characters (for example keywords such as define, if, let, or void) from which syntactically valid programs are constructed.

Below is a simple grammar, based on Lisp, which defines productions for the syntactic categories expression, atom, number, symbol, and list:

expression ::= atom | list
atom ::= number | symbol
number ::= [+-]?['0'-'9']+
symbol ::= ['A'-'Z''a'-'z'].*
list ::= '(' expression* ')'

This grammar specifies the following:

* an expression is either an atom or a list;
* an atom is either a number or a symbol;
* a number is an unbroken sequence of one or more decimal digits, optionally preceded by a plus or minus sign;
* a symbol is a letter followed by zero or more of any characters (excluding whitespace); and
* a list is a matched pair of parentheses, with zero or more expressions inside it.

Here the decimal digits, upper- and lower-case characters, and parentheses are terminal symbols.

The following are examples of well-formed token sequences in this grammar: '12345', '()', '(a b c232 (1))'

The grammar needed to specify a programming language can be classified by its position in the Chomsky hierarchy. The syntax of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars.[2] However, there are exceptions. In some languages like Perl and Lisp the specification (or implementation) of the language allows constructs that execute during the parsing phase. Furthermore, these languages have constructs that allow the programmer to alter the behavior of the parser. This combination effectively blurs the distinction between parsing and execution, and makes syntax analysis an undecidable problem in these languages, meaning that the parsing phase may not finish. For example, in Perl it is possible to execute code during parsing using a BEGIN statement, and Perl function prototypes may alter the syntactic interpretation, and possibly even the syntactic validity of the remaining code.[3] Similarly, Lisp macros introduced by the defmacro syntax also execute during parsing, meaning that a Lisp compiler must have an entire Lisp run-time system present. In contrast C macros are merely string replacements, and do not require code execution.[4][5]

Syntax versus semantics

The syntax of a language describes the form of a valid program, but does not provide any information about the meaning of the program or the results of executing that program. The meaning given to a combination of symbols is handled by semantics (either formal or hard-coded in a reference implementation). Not all syntactically correct programs are semantically correct. Many syntactically correct programs are nonetheless ill-formed, per the language's rules; and may (depending on the language specification and the soundness of the implementation) result in an error on translation or execution. In some cases, such programs may exhibit undefined behavior. Even when a program is well-defined within a language, it may still have a meaning that is not intended by the person who wrote it.

Using natural language as an example, it may not be possible to assign a meaning to a grammatically correct sentence or the sentence may be false:

* "Colorless green ideas sleep furiously." is grammatically well-formed but has no generally accepted meaning.
* "John is a married bachelor." is grammatically well-formed but expresses a meaning that cannot be true.

The following C language fragment is syntactically correct, but performs an operation that is not semantically defined (because p is a null pointer, the operations p->real and p->im have no meaning):

complex *p = NULL;
complex abs_p = sqrt (p->real * p->real + p->im * p->im);

raid

2010-05-19T00:49:00.000-07:00

RAID

From Wikipedia, the free encyclopedia

RAID, an acronym for redundant array of independent disks or also known as redundant array of inexpensive disks, is a technology that allows high levels of storage reliability from low-cost and less reliable PC-class disk-drive components, via the technique of arranging the devices into arrays for redundancy . This concept was first defined by David A. Patterson , Garth A. Gibson , and Randy Katz at the University of California, Berkeley in 1987 as redundant array of inexpensive disks.^[1] Marketers representing industry RAID manufacturers later reinvented the term to describe a redundant array of independent disks as a means of dissociating a low-cost expectation from RAID technology.^[2]

RAID is now used as an umbrella term for computer data storage schemes that can divide and replicate data among multiple hard disk drives. The different schemes/architectures are named by the word RAID followed by a number, as in RAID 0, RAID 1, etc. RAID's various designs involve two key design goals: increase data reliability and/or increase input/output performance. When multiple physical disks are set up to use RAID technology, they are said to be in a RAID array^[3]. This array distributes data across multiple disks, but the array is seen by the computer user and operating system as one single disk. RAID can be set up to serve several different purposes.

[*] Principles

RAID combines two or more physical hard disks into a single logical unit using special hardware or software. Hardware solutions are often designed to present themselves to the attached system as a single hard drive, so that the operating system would be unaware of the technical workings. For example, if one were to configure a hardware-based RAID-5 volume using three 250 GB hard drives (two drives for data, and one for parity ), the operating system would be presented with a single 500 GB volume. Software solutions are typically implemented in the operating system and would present the RAID volume as a single drive to applications running within the operating system.

There are three key concepts in RAID: mirroring , the writing of identical data to more than one disk; striping , the splitting of data across more than one disk; and error correction , where redundant parity data is stored to allow problems to be detected and possibly repaired (known as fault tolerance ). Different RAID schemes use one or more of these techniques, depending on the system requirements. The purpose of using RAID is to improve reliability and availability of data, ensuring that important data is not harmed in case of hardware failure, and/or to increase the speed of file input/output .

Each RAID scheme affects reliability and performance in different ways. Every additional disk included in an array increases the likelihood that one will fail, but by using error checking and/or mirroring, the array as a whole can be made more reliable by the ability to survive and recover from a failure. Basic mirroring can speed up the reading of data, as a system can read different data from multiple disks at the same time, but it may be slow for writing if the configuration requires that all disks must confirm that the data is correctly written. Striping, often used for increasing performance, writes each bit to a different disk, allowing the data to be reconstructed from multiple disks faster than a single disk could send the same data. Error checking typically will slow down performance as data needs to be read from multiple places and then compared. The design of any RAID scheme is often a compromise in one or more respects, and understanding the requirements of a system is important. Modern disk arrays typically provide the facility to select an appropriate RAID configuration.

[*] Organization

Organizing disks into a redundant array decreases the usable storage capacity. For instance, a 2-disk RAID 1 array loses half of the total capacity that would have otherwise been available using both disks independently, and a RAID 5 array with several disks loses the capacity of one disk. Other types of RAID arrays are arranged, for example, so that they are faster to write to and read from than a single disk.

There are various combinations of these approaches giving different trade-offs of protection against data loss, capacity, and speed. RAID levels 0, 1, and 5 are the most commonly found, and cover most requirements.

[*] Standard levels

Main article: Standard RAID levels

A number of standard schemes have evolved which are referred to as levels. There were five RAID levels originally conceived, but many more variations have evolved, notably several nested levels and many non-standard levels (mostly proprietary ).

Following is a brief summary of the most commonly used RAID levels.^[4] Space efficiency is given as amount of storage space available in an array of n disks, in multiples of the capacity of a single drive. For example if an array holds n=5 drives of 250GB and efficiency is n-1 then available space is 4 times 250GB or roughly 1TB.

Level	Description	Minimum # of disks	Space Efficiency	Fault Tolerance
RAID 0	Striped set without parity or mirroring. Provides improved performance and additional storage but no redundancy or fault tolerance. Because there is no redundancy, this level is not actually a Redundant Array of Independent Disks, i.e. not true RAID. However, because of the similarities to RAID (especially the need for a controller to distribute data across multiple disks), simple stripe sets are normally referred to as RAID 0. Any disk failure destroys the array, which has greater consequences with more disks in the array (at a minimum, catastrophic data loss is twice as severe compared to single drives without RAID). A single disk failure destroys the entire array because when data is written to a RAID 0 drive, the data is broken into fragments. The number of fragments is dictated by the number of disks in the array. The fragments are written to their respective disks simultaneously on the same sector. This allows smaller sections of the entire chunk of data to be read off the drive in parallel, increasing bandwidth. RAID 0 does not implement error checking so any error is unrecoverable. More disks in the array means higher bandwidth, but greater risk of data loss.	2	n	0 (none)
RAID 1	Mirrored set without parity or striping. Provides fault tolerance from disk errors and failure of all but one of the drives. Increased read performance occurs when using a multi-threaded operating system that supports split seeks, as well as a very small performance reduction when writing. Array continues to operate so long as at least one drive is functioning. Using RAID 1 with a separate controller for each disk is sometimes called duplexing.	2	1 (size of the smallest disk)	n-1 disks
RAID 2	Hamming code parity. Disks are synchronized and striped in very small stripes, often in single bytes/words. Hamming codes error correction is calculated across corresponding bits on disks, and is stored on multiple parity disks.	3
RAID 3	Striped set with dedicated parity or bit interleaved parity or byte level parity. This mechanism provides fault tolerance similar to RAID 5. However, because the stripe across the disks is much smaller than a filesystem block, reads and writes to the array perform like a single drive with a high linear write performance. For this to work properly, the drives must have synchronised rotation. If one drive fails, performance is not affected.	3	n-1	1 disk
RAID 4	Block level parity. Identical to RAID 3, but does block-level striping instead of byte-level striping. In this setup, files can be distributed between multiple disks. Each disk operates independently which allows I/O requests to be performed in parallel, though data transfer speeds can suffer due to the type of parity. The error detection is achieved through dedicated parity and is stored in a separate, single disk unit.	3	n-1	1 disk
RAID 5	Striped set with distributed parity or interleave parity. Distributed parity requires all drives but one to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure. Upon drive failure, any subsequent reads can be calculated from the distributed parity such that the drive failure is masked from the end user. The array will have data loss in the event of a second drive failure and is vulnerable until the data that was on the failed drive is rebuilt onto a replacement drive. A single drive failure in the set will result in reduced performance of the entire set until the failed drive has been replaced and rebuilt.	3	n-1	1 disk
RAID 6	Striped set with dual distributed parity. Provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical, especially for high availability systems. This becomes increasingly important because large-capacity drives lengthen the time needed to recover from the failure of a single drive. Single parity RAID levels are vulnerable to data loss until the failed drive is rebuilt: the larger the drive, the longer the rebuild will take. Dual parity gives time to rebuild the array without the data being at risk if a (single) additional drive fails before the rebuild is complete.	4	n-2	2 disks

[*] Nested (hybrid) RAID

Main article: Nested RAID levels

In what was originally termed hybrid RAID,^[5] many storage controllers allow RAID levels to be nested. The elements of a RAID may be either individual disks or RAIDs themselves. Nesting more than two deep is unusual.

As there is no basic RAID level numbered larger than 9, nested RAIDs are usually unambiguously described by concatenating the numbers indicating the RAID levels, sometimes with a "+" in between. For example, RAID 10 (or RAID 1+0) consists of several level 1 arrays of physical drives, each of which is one of the "drives" of a level 0 array striped over the level 1 arrays. It is not called RAID 01, to avoid confusion with RAID 1, or indeed, RAID 01 . When the top array is a RAID 0 (such as in RAID 10 and RAID 50) most vendors omit the "+", though RAID 5+0 is clearer.

The key difference from RAID 0+1 is that RAID 1+0 creates a striped set from a series of mirrored drives. In a failed disk situation, RAID 1+0 performs better because all the remaining disks continue to be used. The array can sustain multiple drive losses so long as no mirror loses all its drives.

RAID 5+1: mirror striped set with distributed parity (some manufacturers label this as RAID 53).

[*] New RAID classification

In 1996, the RAID Advisory Board introduced an improved classification of RAID systems. It divides RAID into three types: Failure-resistant disk systems (that protect against data loss due to disk failure), failure-tolerant disk systems (that protect against loss of data access due to failure of any single component), and disaster-tolerant disk systems (that consist of two or more independent zones, either of which provides access to stored data).

The original "Berkeley" RAID classifications are still kept as an important historical reference point and also to recognize that RAID Levels 0-6 successfully define all known data mapping and protection schemes for disk. Unfortunately, the original classification caused some confusion due to assumption that higher RAID levels imply higher redundancy and performance. This confusion was exploited by RAID system manufacturers, and gave birth to the products with such names as RAID-7, RAID-10, RAID-30, RAID-S, etc. The new system describes the data availability characteristics of the RAID system rather than the details of its implementation.

The next list provides criteria for all three classes of RAID:

- Failure-resistant disk systems (FRDS) (meets a minimum of criteria 1 - 6):

1. Protection against data loss and loss of access to data due to disk drive failure
2. Reconstruction of failed drive content to a replacement drive
3. Protection against data loss due to a "write hole"
4. Protection against data loss due to host and host I/O bus failure
5. Protection against data loss due to replaceable unit failure
6. Replaceable unit monitoring and failure indication

- Failure-tolerant disk systems (FTDS) (meets a minimum of criteria 7 - 15 ):

7. Disk automatic swap and hot swap
8. Protection against data loss due to cache failure
9. Protection against data loss due to external power failure
10. Protection against data loss due to a temperature out of operating range
11. Replaceable unit and environmental failure warning
12. Protection against loss of access to data due to device channel failure
13. Protection against loss of access to data due to controller module failure
14. Protection against loss of access to data due to cache failure
15. Protection against loss of access to data due to power supply failure

- Disaster-tolerant disk systems (DTDS) (meets a minimum of criteria 16 - 21):

16. Protection against loss of access to data due to host and host I/O bus failure
17. Protection against loss of access to data due to external power failure
18. Protection against loss of access to data due to component replacement
19. Protection against loss of data and loss of access to data due to multiple disk failure
20. Protection against loss of access to data due to zone failure
21. Long-distance protection against loss of data due to zone failure

[*] Non-standard levels

Main article: Non-standard RAID levels

Many configurations other than the basic numbered RAID levels are possible, and many companies, organizations, and groups have created their own non-standard configurations, in many cases designed to meet the specialised needs of a small niche group. Most of these non-standard RAID levels are proprietary .

[*] Parity calculation; rebuilding failed drives

Parity data in a RAID environment is calculated using the Boolean XOR function. For example, here is a simple RAID 4 three-disk setup consisting of two drives that hold 8 bits of data each and a third drive that will be used to hold parity data.

Drive 1: 01101101
Drive 2: 11010100

To calculate parity data for the two drives, a XOR is performed on their data.
i.e. 01101101 XOR 11010100 = 10111001

The resulting parity data, 10111001, is then stored on Drive 3, the dedicated parity drive.

Should any of the three drives fail, the contents of the failed drive can be reconstructed on a replacement (or "hot spare") drive by subjecting the data from the remaining drives to the same XOR operation. If Drive 2 were to fail, its data could be rebuilt using the XOR results of the contents of the two remaining drives, Drive 3 and Drive 1:

Drive 3: 10111001
Drive 1: 01101101

i.e. 10111001 XOR 01101101 = 11010100

The result of that XOR calculation yields Drive 2's contents. 11010100 is then stored on Drive 2, fully repairing the array. This same XOR concept applies similarly to larger arrays, using any number of disks. In the case of a RAID 3 array of 12 drives, 11 drives participate in the XOR calculation shown above and yield a value that is then stored on the dedicated parity drive.

Another way of saying this is:

Basically, all it’s doing on the 3rd (recovery) drive is telling you whether the data on the first 2 drives is equal or not, 0 being yes, and 1 being no. Therefore, pretend that the second drive is missing. Drive 1 says 1, and Drive 3 says that Drive 1 and 2 are not the same value (1) so drive 2 must be a 0. If Drive 3 said they were the same value (0) then drive 2 must be a 0. That’s how it’s recalculated. It also tells you how the number of missing drives can’t exceed the number of recovery volumes. If drives 1 and 2 were both missing, and drive 3 said 0 (they’re the same) it still wouldn’t know if they’re both 0’s or if they’re both 1’s. If drive 3 said 1 (they’re different) you wouldn’t know whether drive 1 was 0 and drive 2 was 1, or if it was the other way around.

[*] RAID is not data backup

A RAID system used as a main drive is not a replacement for backing up data. Data may become damaged or destroyed without harm to the drive(s) on which they are stored. For example, some of the data may be overwritten by a system malfunction; a file may be damaged or deleted by user error or malice and not noticed for days or weeks. RAID can also be overwhelmed by catastrophic failure that exceeds its recovery capacity and, of course, the entire array is at risk of physical damage by fire, natural disaster, or human forces. RAID is also vulnerable to controller failure since it is not always possible to migrate a RAID to a new controller without data loss ^[9].

RAID drives can make excellent backup drives, when employed as backup devices to main storage, and particularly when located offsite from the main systems. However, the use of RAID as the main storage solution cannot replace backups.

[*] Implementations

(Specifically, the section comparing hardware / software raid)

The distribution of data across multiple drives can be managed either by dedicated hardware or by software . When done in software the software may be part of the operating system or it may be part of the firmware and drivers supplied with the card.

[*] Operating system based ("software RAID")

Software implementations are now provided by many operating systems . A software layer sits above the (generally block -based) disk device drivers and provides an abstraction layer between the logical drives (RAIDs) and physical drives . Most common levels are RAID 0 (striping across multiple drives for increased space and performance) and RAID 1 (mirroring two drives), followed by RAID 1+0, RAID 0+1, and RAID 5 (data striping with parity) are supported.

Software RAID has advantages and disadvantages compared to hardware RAID. The software must run on a host server attached to storage, and server's processor must dedicate processing time to run the RAID software. The additional processing capacity required for RAID 0 and RAID 1 is low, but parity-based arrays require more complex data processing during write or integrity-checking operations. As the rate of data processing increases with the number of disks in the array, so does the processing requirement. Furthermore all the buses between the processor and the disk controller must carry the extra data required by RAID which may cause congestion.

Over the history of hard disk drives, the increase in speed of commodity CPUs has been consistently greater than the increase in speed of hard disk drive throughput^[18]. Thus, over-time for a given number of hard disk drives, the percentage of host CPU time required to saturate a given number of hard disk drives has been dropping. e.g. The Linux software md RAID subsystem is capable of calculating parity information at 6GB/s (100% usage of a single core on a 2.1 GHz Intel "Core2" CPU as of Linux v2.6.26). A three-drive RAID5 array using hard disks capable of sustaining a write of 100MB/s will require parity to be calculated at the rate of 200MB/s. This will require the resources of just over 3% of a single CPU core during write operations (parity does not need to be calculated for read operations on a RAID5 array, unless a drive has failed).

Software RAID implementations may employ more sophisticated algorithms than hardware RAID implementations (for instance with respect to disk scheduling and command queueing), and thus may be capable of increased performance.

Another concern with operating system-based RAID is the boot process. It can be difficult or impossible to set up the boot process such that it can fail over to another drive if the usual boot drive fails. Such systems can require manual intervention to make the machine bootable again after a failure. There are exceptions to this, such as the LILO bootloader for Linux, loader for FreeBSD^[19] , and some configurations of the GRUB bootloader natively understand RAID-1 and can load a kernel. If the BIOS recognizes a broken first disk and refers bootstrapping to the next disk, such a system will come up without intervention, but the BIOS might or might not do that as intended. A hardware RAID controller typically has explicit programming to decide that a disk is broken and fall through to the next disk.

Hardware RAID controllers can also carry battery-powered cache memory. For data safety in modern systems the user of software RAID might need to turn the write-back cache on the disk off (but some drives have their own battery/capacitors on the write-back cache, a UPS, and/or implement atomicity in various ways, etc). Turning off the write cache has a performance penalty that can, depending on workload and how well supported command queuing in the disk system is, be significant. The battery backed cache on a RAID controller is one solution to have a safe write-back cache.

Finally operating system-based RAID usually uses formats specific to the operating system in question so it cannot generally be used for partitions that are shared between operating systems as part of a multi-boot setup. However, this allows RAID disks to be moved from one computer to a computer with an operating system or file system of the same type, which can be more difficult when using hardware RAID (e.g. #1: When one computer uses a hardware RAID controller from one manufacturer and another computer uses a controller from a different manufacturer, drives typically cannot be interchanged. e.g. #2: If the hardware controller 'dies' before the disks do, data may become unrecoverable unless a hardware controller of the same type is obtained, unlike with firmware-based or software-based RAID).

Most operating system-based implementations allow RAIDs to be created from partitions rather than entire physical drives. For instance, an administrator could divide an odd number of disks into two partitions per disk, mirror partitions across disks and stripe a volume across the mirrored partitions to emulate IBM's RAID 1E configuration . Using partitions in this way also allows mixing reliability levels on the same set of disks. For example, one could have a very robust RAID 1 partition for important files, and a less robust RAID 5 or RAID 0 partition for less important data. (Some BIOS-based controllers offer similar features, e.g. Intel Matrix RAID .) Using two partitions on the same drive in the same RAID is, however, dangerous. (e.g. #1: Having all partitions of a RAID-1 on the same drive will, obviously, make all the data inaccessible if the single drive fails. e.g. #2: In a RAID 5 array composed of four drives 250 + 250 + 250 + 500 GB, with the 500-GB drive split into two 250 GB partitions, a failure of this drive will remove two partitions from the array, causing all of the data held on it to be lost).

[*] Hardware-based

Hardware RAID controllers use different, proprietary disk layouts, so it is not usually possible to span controllers from different manufacturers. They do not require processor resources, the BIOS can boot from them, and tighter integration with the device driver may offer better error handling.

A hardware implementation of RAID requires at least a special-purpose RAID controller . On a desktop system this may be a PCI expansion card , PCI-e expansion card or built into the motherboard . Controllers supporting most types of drive may be used – IDE/ATA , SATA , SCSI , SSA , Fibre Channel , sometimes even a combination. The controller and disks may be in a stand-alone disk enclosure , rather than inside a computer. The enclosure may be directly attached to a computer, or connected via SAN . The controller hardware handles the management of the drives, and performs any parity calculations required by the chosen RAID level.

Most hardware implementations provide a read/write cache , which, depending on the I/O workload, will improve performance. In most systems the write cache is non-volatile (i.e. battery-protected), so pending writes are not lost on a power failure.

Hardware implementations provide guaranteed performance, add no overhead to the local CPU complex and can support many operating systems, as the controller simply presents a logical disk to the operating system.

Hardware implementations also typically support hot swapping, allowing failed drives to be replaced while the system is running.

However, hardware RAID controllers are mostly slower than software RAID due to a dedicated CPU on the controller card, which isn't as fast as a real CPU in a computer/server . More expensive RAID controllers have faster CPUs. If you buy a hardware RAID controller, checkout the specs and look for throughput speed.

[*] Firmware/driver-based RAID ("FakeRAID")

Operating system-based RAID doesn't always protect the boot process and is generally impractical on desktop versions of Windows (as described above). Hardware RAID controllers are expensive and proprietary. To fill this gap, cheap "RAID controllers" were introduced that do not contain a RAID controller chip, but simply a standard disk controller chip with special firmware and drivers. During early stage bootup the RAID is implemented by the firmware; when a protected-mode operating system kernel such as Linux or a modern version of Microsoft Windows is loaded the drivers take over.

These controllers are described by their manufacturers as RAID controllers, and it is rarely made clear to purchasers that the burden of RAID processing is borne by the host computer's central processing unit, not the RAID controller itself, thus introducing the aforementioned CPU overhead from which hardware controllers don't suffer. Firmware controllers often can only use certain types of hard drives in their RAID arrays (e.g. SATA for Intel Matrix RAID ), as there is neither SCSI nor PATA support in modern Intel ICH southbridges ; however, motherboard makers implement RAID controllers outside of the southbridge on some motherboards. Before their introduction, a "RAID controller" implied that the controller did the processing, and the new type has become known by some as "fake RAID" even though the RAID itself is implemented correctly. Adaptec calls them "HostRAID".

[*] Network-attached storage

Main article: Network-attached storage

While not directly associated with RAID, Network-attached storage (NAS) is an enclosure containing disk drives and the equipment necessary to make them available over a computer network , usually Ethernet . The enclosure is basically a dedicated computer in its own right, designed to operate over the network without screen or keyboard. It contains one or more disk drives; multiple drives may be configured as a RAID.

[*] Hot spares

Both hardware and software RAIDs with redundancy may support the use of hot spare drives, a drive physically installed in the array which is inactive until an active drive fails, when the system automatically replaces the failed drive with the spare, rebuilding the array with the spare drive included. This reduces the mean time to recovery (MTTR), though it doesn't eliminate it completely. Subsequent additional failure(s) in the same RAID redundancy group before the array is fully rebuilt can result in loss of the data; rebuilding can take several hours, especially on busy systems.

Rapid replacement of failed drives is important as the drives of an array will all have had the same amount of use, and may tend to fail at about the same time rather than randomly.^[^{citation needed]} RAID 6 without a spare uses the same number of drives as RAID 5 with a hot spare and protects data against simultaneous failure of up to two drives, but requires a more advanced RAID controller. Further, a hot spare can be shared by multiple RAID sets.

[*] Reliability terms

Failure rate

Two different kinds of failure rates are applicable to RAID systems. Logical failure is defined as the loss of a single drive and its rate is equal to the sum of individual drives' failure rates. System failure is defined as loss of data and its rate will depend on the type of RAID. For RAID 0 this is equal to the logical failure rate, as there is no redundancy. For other types of RAID, it will be less than the logical failure rate, potentially approaching zero, and its exact value will depend on the type of RAID, the number of drives employed, and the vigilance and alacrity of its human administrators.

Mean time to data loss (MTTDL)

In this context, the average time before a loss of data in a given array.^[20]. Mean time to data loss of a given RAID may be higher or lower than that of its constituent hard drives, depending upon what type of RAID is employed. The referenced report assumes times to data loss are exponentially distributed. This means 63.2% of all data loss will occur between time 0 and the MTTDL.

Mean time to recovery (MTTR)

In arrays that include redundancy for reliability, this is the time following a failure to restore an array to its normal failure-tolerant mode of operation. This includes time to replace a failed disk mechanism as well as time to re-build the array (i.e. to replicate data for redundancy).

Unrecoverable bit error rate (UBE)

This is the rate at which a disk drive will be unable to recover data after application of cyclic redundancy check (CRC) codes and multiple retries.

Write cache reliability

Some RAID systems use RAM write cache to increase performance. A power failure can result in data loss unless this sort of disk buffer is supplemented with a battery to ensure that the buffer has enough time to write from RAM back to disk.

Atomic write failure

Also known by various terms such as torn writes, torn pages, incomplete writes, interrupted writes, non-transactional, etc.

[*] Problems with RAID

[*] Correlated failures

The theory behind the error correction in RAID assumes that failures of drives are independent. Given these assumptions it is possible to calculate how often they can fail and to arrange the array to make data loss arbitrarily improbable.

In practice, the drives are often the same ages, with similar wear. Since many drive failures are due to mechanical issues which are more likely on older drives, this violates those assumptions and failures are in fact statistically correlated. In practice then, the chances of a second failure before the first has been recovered is not nearly as unlikely as might be supposed, and data loss can, in practice, occur at significant rates.^[21]

A common misconception is that "server-grade" drives fail less frequently than consumer-grade drives. Two independent studies, one by Carnegie Mellon University and the other by Google , have shown that the “grade” of the drive does not relate to failure rates.^[22][23]

[*] Atomicity

This is a little understood and rarely mentioned failure mode for redundant storage systems that do not utilize transactional features. Database researcher Jim Gray wrote "Update in Place is a Poison Apple"^[24] during the early days of relational database commercialization. However, this warning largely went unheeded and fell by the wayside upon the advent of RAID, which many software engineers mistook as solving all data storage integrity and reliability problems. Many software programs update a storage object "in-place"; that is, they write a new version of the object on to the same disk addresses as the old version of the object. While the software may also log some delta information elsewhere, it expects the storage to present "atomic write semantics," meaning that the write of the data either occurred in its entirety or did not occur at all.

However, very few storage systems provide support for atomic writes, and even fewer specify their rate of failure in providing this semantic. Note that during the act of writing an object, a RAID storage device will usually be writing all redundant copies of the object in parallel, although overlapped or staggered writes are more common when a single RAID processor is responsible for multiple drives. Hence an error that occurs during the process of writing may leave the redundant copies in different states, and furthermore may leave the copies in neither the old nor the new state. The little known failure mode is that delta logging relies on the original data being either in the old or the new state so as to enable backing out the logical change, yet few storage systems provide an atomic write semantic on a RAID disk.

While the battery-backed write cache may partially solve the problem, it is applicable only to a power failure scenario.

Since transactional support is not universally present in hardware RAID, many operating systems include transactional support to protect against data loss during an interrupted write. Novell Netware, starting with version 3.x, included a transaction tracking system. Microsoft introduced transaction tracking via the journaling feature in NTFS . Ext4 has journaling with checksums; ext3 has journaling without checksums but an "append-only" option, or ext3COW (Copy on Write). If the journal itself in a filesystem is corrupted though, this can be problematic. The journaling in NetApp WAFL file system gives atomicity by never updating the data in place, as does ZFS . An alternative method to journaling is soft updates , which are used in some BSD-derived system's implementation of UFS .

This can present as a sector read failure. Some RAID implementations protect against this failure mode by remapping the bad sector , using the redundant data to retrieve a good copy of the data, and rewriting that good data to the newly mapped replacement sector. The UBE (Unrecoverable Bit Error) rate is typically specified at 1 bit in 10¹⁵ for enterprise class disk drives (SCSI , FC , SAS ) , and 1 bit in 10¹⁴ for desktop class disk drives (IDE/ATA/PATA, SATA). Increasing disk capacities and large RAID 5 redundancy groups have led to an increasing inability to successfully rebuild a RAID group after a disk failure because an unrecoverable sector is found on the remaining drives. Double protection schemes such as RAID 6 are attempting to address this issue, but suffer from a very high write penalty.

[*] Write cache reliability

The disk system can acknowledge the write operation as soon as the data is in the cache, not waiting for the data to be physically written. This typically occurs in old, non-journaled systems such as FAT32, or if the Linux/Unix "writeback" option is chosen without any protections like the "soft updates" option (to promote I/O speed whilst trading-away data reliability). A power outage or system hang such as a BSOD can mean a significant loss of any data queued in such a cache.

Often a battery is protecting the write cache, mostly solving the problem. If a write fails because of power failure, the controller may complete the pending writes as soon as restarted. This solution still has potential failure cases: the battery may have worn out, the power may be off for too long, the disks could be moved to another controller, the controller itself could fail. Some disk systems provide the capability of testing the battery periodically, however this leaves the system without a fully charged battery for several hours.

An additional concern about write cache reliability exists, specifically regarding devices equipped with a write-back cache—a caching system which reports the data as written as soon as it is written to cache, as opposed to the non-volatile medium.^[25] The safer cache technique is write-through, which reports transactions as written when they are written to the non-volatile medium.

[*] Equipment compatibility

The disk formats on different RAID controllers are not necessarily compatible, so that it may not be possible to read a RAID on different hardware. Consequently a non-disk hardware failure may require using identical hardware to recover the data. Software RAID however, such as implemented in the Linux kernel, alleviates this concern, as the setup is not hardware dependent, but runs on ordinary disk controllers. Additionally, Software RAID1 disks (and some hardware RAID1 disks, for example Silicon Image 5744) can be read like normal disks, so no RAID system is required to retrieve the data. Data recovery firms typically have a very hard time recovering data from RAID drives, with the exception of RAID1 drives with conventional data structure.

[*] Data recovery in the event of a failed array

With larger disk capacities the odds of a disk failure during rebuild are not negligible. In that event the difficulty of extracting data from a failed array must be considered. Only RAID 1 stores all data on each disk. Although it may depend on the controller, some RAID 1 disks can be read as a single conventional disk. This means a dropped RAID 1 disk, although damaged, can often be reasonably easily recovered using a software recovery program or CHKDSK. If the damage is more severe, data can often be recovered by professional drive specialists. RAID5 and other striped or distributed arrays present much more formidable obstacles to data recovery in the event the array goes down.

[*] Drive error recovery algorithms

Many modern drives have internal error recovery algorithms that can take upwards of a minute to recover and re-map data that the drive fails to easily read. Many RAID controllers will drop a non-responsive drive in 8 seconds or so. This can cause the array to drop a good drive because it has not been given enough time to complete its internal error recovery procedure, leaving the rest of the array vulnerable. So-called enterprise class drives limit the error recovery time and prevent this problem, but desktop drives can be quite risky for this reason. A fix is known for Western Digital drives. A utility called WDTLER.exe can limit the error recovery time of a Western Digital desktop drive so that it will not be dropped from the array for this reason. The utility enables TLER (time limited error recovery) which limits the error recovery time to 7 seconds. <--"UPDATE" As of October 2009 Western Digital has locked out this feature in their desktop drives such as the Caviar Black. It is said that if you try to run the WDTLER program you may actually damage the firmware of the drive. "UPDATE"--> Western Digital enterprise class drives are shipped from the factory with TLER enabled to prevent being dropped from RAID arrays. Similar technologies are used by Seagate, Samsung, and Hitachi.

[*] Increasing recovery time

Drive capacity has grown at a much faster rate than transfer speed, and error rates have only fallen a little in comparison. Therefore, larger capacity drives may take hours, if not days, to rebuild. The re-build time is also limited if the entire array is still in operation at reduced capacity.^[26] Given a RAID array with only one disk of redundancy (RAIDs 3, 4, and 5), a second failure would cause complete failure of the array, as the mean time between failure (MTBF) is high.^[27]

[*] Other problems and viruses

While RAID may protect against physical drive failure, the data is still exposed to operator, software, hardware and virus destruction. Many studies^[28] cite operator fault as the most common source of malfunction, such as a server operator replacing the incorrect disk in a faulty RAID array, and disabling the system (even temporarily) in the process.^[29] Most well-designed systems include separate backup systems that hold copies of the data, but don't allow much interaction with it. Most copy the data and remove the copy from the computer for safe storage.

[*] History

Norman Ken Ouchi at IBM was awarded a 1978 U.S. patent 4,092,732^[30] titled "System for recovering data stored in failed memory unit." The claims for this patent describe what would later be termed RAID 5 with full stripe writes. This 1978 patent also mentions that disk mirroring or duplexing (what would later be termed RAID 1) and protection with dedicated parity (that would later be termed RAID 4) were prior art at that time.

The term RAID was first defined by David A. Patterson , Garth A. Gibson and Randy Katz at the University of California, Berkeley, in 1987. They studied the possibility of using two or more drives to appear as a single device to the host system and published a paper: "A Case for Redundant Arrays of Inexpensive Disks (RAID)" in June 1988 at the SIGMOD conference.^[1]

This specification suggested a number of prototype RAID levels, or combinations of drives. Each had theoretical advantages and disadvantages. Over the years, different implementations of the RAID concept have appeared. Most differ substantially from the original idealized RAID levels, but the numbered names have remained. This can be confusing, since one implementation of RAID 5, for example, can differ substantially from another. RAID 3 and RAID 4 are often confused and even used interchangeably.

One of the early uses of RAID 0 and 1 was the Crosfield Electronics Studio 9500 page layout system based on the Python workstation. The Python workstation was a Crosfield managed international development using PERQ 3B electronics, benchMark Technology's Viper display system and Crosfield's own RAID and fibre-optic network controllers. RAID 0 was particularly important to these workstations as it dramatically speeded image manipulation for the pre-press markets. Volume production started in Peterborough, England in early 1987.

[*] Non-RAID drive architectures

Main article: Non-RAID drive architectures

Non-RAID drive architectures also exist, and are often referred to, similarly to RAID, by standard acronyms, several tongue-in-cheek. A single drive is referred to as a SLED (Single Large Expensive Drive), by contrast with RAID, while an array of drives without any additional control (accessed simply as independent drives) is referred to as a JBOD (Just a Bunch Of Disks). Simple concatenation is referred to a SPAN, or sometimes as JBOD, though this latter is proscribed in careful use, due to the alternative meaning just cited.

digtal

2010-05-13T01:33:00.000-07:00

ALT tab

2010-04-26T23:57:00.000-07:00

Alt - Tab

Alt-Tab is the common name for a keyboard shortcut on Microsoft Windows Windows 3.0 onwards used for switching between top-level windows without using the mouse; hence it was named Task Switcher (Flip in Windows Vista). Casual users may press Alt-⇆ Tab to
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alternate between the two most recent tasks, but used to its full potential, Alt-Tab can switch to any running program. The list of tasks is kept in an order with the most recently used tasks at the front. Tab does not need to be pressed as many times to move the task selection cursor from the front of the list to a nearer task—the more recently used, the easier to get back.

Since its introduction in Windows, the Alt-Tab keyboard combination has also been incorporated to other widely used operating systems, such as Mac OS X and free software desktop environments such as KDE and GNOME.

Precise behavior

Alt-Tab is accessed by a somewhat unusual application of the keyboard. First the Alt key is pressed and held down. While Alt is down, Tab may be pressed and released , sometimes combined with Shift if desired, to cycle the cursor through a list of tasks. A special task selection window appears the first time Tab is pressed with Alt down. The release of the Alt key is the act that closes the task selection window and switches to the selected task.

The fact that the menu is held open by keeping Alt pressed may seem unusual, given the way the modifier keys (Ctrl, Alt, and Shift) are typically used, but the behavior is quite intuitive and users quickly become accustomed to it[who?].

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The full capabilities of Alt-Tab are learned intuitively by many users. Its behavior has undergone few changes over the years and has many subtle features that define it.

The behavior can be defined by these rules:

* As long as there is more than one task window, the task list appears as soon as Tab is pressed with Alt down.
* The task list remains open until Alt is released.
* Tab moves the cursor forward in the list; Shift-Tab moves it backward. In the event that there are many windows, Tab or Shift-Tab can be allowed to autorepeat.
* With the initial press of Tab or Shift-Tab, the square selection cursor is placed onto the window immediately following or immediately before the active one. If there are no topmost windows above the active window, an initial Shift-Tab wraps the cursor around to the end of the list.
* Esc while Alt is still down aborts the switch.
* The windows are listed by their "Z-order". Any windows which are "always on top" are kept at the head of the Z-order sequence and are listed first, followed by the current window and the windows underneath it.
* Switching to a window moves it to the top of the Z-order sequence, moving it to the front of the list, with the exception that "always on top" windows remain topmost and at the front of the list.
* When the Alt-Tab window is not in use, Alt-Esc lowers a window, placing it at the bottom of the Z-order sequence. This sends it to the end of the list. Alt-Shift-Esc is equivalent to one Alt-Shift-Tab except that minimized windows are selected without being restored.
* Minimizing a window also sends it to the end of the list in the same way as Alt-Esc. Some applications, notably Outlook, violate this.

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Windows Vista changed the default behavior[1] (under most default installations) with its Flip interface. The six most recently used items in the Flip tab-order work as described, then remaining windows are ordered alphabetically by application path (and optionally grouped, depending on the 'group similar taskbar buttons' setting which is enabled by default).

These rules have certain interesting consequences (in the absence of "always on top" windows such as Task Manager):

* Pressing Alt, pressing Tab, releasing Tab, and releasing Alt (the typical way an Alt key combination is performed) will always alternate between the two most recent tasks.
* Alt-Shift-Tab can restore the most recently minimized window. (If there are "always on top" windows, the lowest of these will be selected instead.)
* Pressing Alt-Tab-Tab (two tabs with Alt continuously held down) provides the same feeling of a quick switch back and forth, but with three programs. The three programs are activated in sequence, repeatedly. In general, any number of tabs can be used to achieve this behaviour with any number of windows, though beyond a small number of windows it becomes tedious and is less useful.
* To expel one of three tasks from use in the above situation, minimize that window and Alt-Tab will immediately begin to behave as if the most recent two tasks were the two remaining.
* To abort the Alt-Tab, before releasing Alt one can press Shift-Tab to undo everything. (Or press Esc.)

A list of top-level windows is maintained with a continually updated ordering. When the selector menu is initially activated by Alt plus the first Tab, the list is populated this way:

* All 'always-on-top' top-level windows according to Z-order, front-to-back, if any exist
* All ordinary top-level windows according to Z-order, front-to-back

This list does not change while the selector remains open. On each new invocation of Alt-Tab, the order can change.

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The Apevia MX-Pleasure case is delicately balanced between striking style and outstanding performance. Front panel features two â€œold schoolâ€? gauges with modern blue backlights to monitor temperature and fan speed, fan control, along with an I/O panel (2 USB 2.0 ports and a Firewire). Both front panel and side panel are lockable, for added security. The case come standard with a 80mm side fan, and a 120mm rear fan, both with blue LED lights, to give you strong airflow and cool blue lighting. Your standard ATX, Baby AT, or Micro ATX motherboard and peripherals will have plenty of power with the included 500-watt power supply, and youâ€™ll have plenty of room to for it all, with 7 expansion slots. A tool-less rail system makes it easy to install up to four external 5.25â€? drives, two external 3.5â€? drives, and seven 3.5â€? internal drives. Case feet fold in and out for stability when you need it. Whether youâ€™re building from the ground up, or looking to expand your current system, the MX-Pleasure is an grand blend of style and function. With Power Supply: Yes Power Supply Mounted: Top PSU Main Connector: 20+4Pin Motherboard Compatibility: Standard ATX / Baby AT / Micro ATX With Side Panel Window: No External 5.25" Drive Bays: 4 External 3.5" Drive Bays: 2 Internal 3.5" Drive Bays: 7

freelancer Illustrative examples

Windows may be divided into two categories, 'always-on-top' and ordinary. When a task is switched to, it is moved to the head of its category. For the following example, suppose there are no 'always-on-top' windows. Let A be the current window title. Hold down Alt and press and release Tab once, leaving Alt pressed. The window list comes up. A is guaranteed to be first in the list. Suppose the complete list is A W Z E U B C. The selection cursor will initially be on W. Suppose we want to switch to window U. Without releasing Alt, press Tab three more times and then release Alt. Then hold down Alt and press-release Tab once leaving Alt down. The window list will now show U A W Z E B C. Then Tab over to E and release Alt, selecting window E. Press and hold down Alt and press-release Tab once leaving Alt down. The window list will now show E U A W Z B C. Note that the windows switched to with Alt-Tab (E, U, A) are in order of how recently they were switched to. Now Tab over to A and release Alt. Press and hold down Alt and press-release Tab leaving Alt down. The window list will show A E U W Z B C. The effect of this most-recently-used behavior is that to return to the most recent task, Tab is pressed once, for the second most recent task Tab is pressed twice, and so on for all tasks. The priority of a window in terms of Alt-Tab accessibility is how recently it was used. If A is now minimized, the list will become E U W Z B C A, and if Z is minimized the list becomes E U W B C A Z. Thus minimizing a window mimics the effect of not using it for a long time.

The commonplace alternation between the 2 most recent tasks (using a fast Alt-Tab with all keys released immediately) is precisely a special case of the above behavior. Suppose the windows are A B C and we want to alternate between A and B. Hold Alt while pressing and releasing Tab; continue holding Alt. The list will show A B C and the cursor will initially be over B. When Alt is released B will be selected, Tab having been pressed a total of 1 time, and zero attention to the task selection cursor having been necessary. Again, press and release Tab while holding Alt. The list will show B A C and the cursor will initially be over A. When Alt is released we have switched back to A. Displaying the list again, the order has returned to A B C and this sequence can recur. On close inspection, in the course of typing Alt-Tab and releasing both keys quickly, the task list window can be observed to flicker for a split second, so .

If the user has been switching among 3 applications and wants to dispense with one of them by minimizing, one of the remaining ones will be on top immediately after minimizing, and ordinarily Alt-Tab will alternate between the 2 remaining windows. If a program fails to move to the end of the list when minimized, pressing Alt-Tab once will return to the minimized program. Failures such as this can result in a frenzied reordering of the Alt-Tab list by means of several Alt-Tab-Tab-Tab... sequences to compensate for the program misbehavior. The algorithm for this reshuffling is intuitive after using Alt-Tab for a long time.

If the user attempts to switch to an application using Alt-Tab but the application fails to update its place in the z-order (for example, if its window procedure is hung), then the next time Alt-Tab is invoked, the task selection cursor may initially point unexpectedly far into the list of icons, just past the application in question, which will not have been moved to the head of the list.

Applications have some say in where they are located in the Alt-Tab order. The list of windows is altered by the creation and destruction of windows, programmatic hiding, showing, raising, and lowering of windows, and alterations to the window z-order [2] .

LIAN LI PC-60BPLUSII W Black Computer Case With Side Panel Window

What goes into your case is more important than the case itself, and Lian-Li hasn't forgotten that. That's why the PC-60B PLUS II is designed to protect its cargo from excess heat with a veritable maelstrom of air. It isn't just that this case has an 80mm fan on the roof and one in the rear, or the 120mm Fan up front and one on the side panel. It is the skill and precision in which they are placed, to make the cooling power of the four fans greater than the sum of its parts. With all of that, you can feel secure filling itâ€™s four external 5.25" and two external 3.5" drive bays, and its ample five internal hard drive bays without fear of blocking air flow to your maxed out ATX motherboard, all seven of its PCI expansion slots full. Your system will remain safe and cool in the hottest action, and your masterpiece will be viewable to all through its high quality acrylic side window. With Power Supply: No Power Supply Mounted: Top Motherboard Compatibility: 12" x 9.6" ATX With Side Panel Window: Yes External 5.25" Drive Bays: 4 External 3.5" Drive Bays: 2 Internal 3.5" Drive Bays: 5 Expansion Slots: 7

The order of the Alt-Tab list corresponds directly to the z-order, once the windows have been sorted according to 'always-on-top' status. Alt-Shift-Esc is equivalent to one Alt-Shift-Tab except that minimized windows are selected without being displayed.[3]
freelancer Windows-specific issues and hacks

Alt-Tab works even if Windows Explorer is no longer running. On Windows NT-based systems, Alt-Tab is managed by CSRSS (Client/Server Runtime Subsystem). It works even when Ctrl-Alt-Del and Ctrl-Shift-Esc (Task Manager) (which are managed by Winlogon) do not.[4]

LIAN LI PC-A05 A Silver Computer Case

Clean modern lines combined with ultra-modern performance, Lian-li's PC-A05-A is the ideal tower. Housing two 5.25" and one 3.5" External drive bays, it saves space by leaving out redundant drive bays made obsolete by today's multipurpose ROM drives. It hasn't forgotten the internal hard drives that are so necessary today, leaving space for three 3.5" internal drives. It also gives easy access to two USB 2.0 ports ,an IEEE 1394 (Firewire) port and two audio ports up front. This case makes cooling a literal breeze. It has two 120mm ball bearing fans: one located in front of the hard drives for intake, and another in the rear of the case for exhaust. This causes a constant cooling cross breeze over all your sensitive equipment protecting them from the ravages of heat. The A05-A supports ATX Motherboards 12" x 9.6" or smaller, with 7 PCI expansion slots in the rear. With Power Supply: No Motherboard Compatibility: 12" x 9.6" ATX With Side Panel Window: No External 5.25" Drive Bays: 2 External 3.5" Drive Bays: 1 Internal 3.5" Drive Bays: 3 Expansion Slots: 7 Front Ports: 2 x USB2.0 ; 2 x Audio ; 1 x IEEE1394

Alt-Tab may be intercepted (or effectively disabled) by means of a low-level keyboard hook.[5] Such a technique is used by applications such as the Virtual Network Computing (VNC) viewer to pass Alt-Tab keystrokes to the remote desktop when the VNC window is active.

Under Windows XP, the Tweak UI PowerToy[6]. can adjust the number of rows and columns in the task list window, or it can be adjusted via a registry edit[7]. This is helpful if there are so many windows that the list would spill over into multiple pages.

Another Microsoft PowerToy, Alt-Tab Replacement[6], is available for Windows XP that displays a screenshot of each application in the task list rather than just its icon, and allows the user to use the mouse to select the desired application. A more advanced version of this functionality, named Windows Flip, is built into Windows Vista.

A number of third-party tools, similar to Alt-Tab Replacement, are also available that add additional functionality to Alt-Tab.

Additionally, Windows Vista allows the user to navigate through the alt-tab menu using mouse or arrow keys.

When the Aero Glass theme is enabled, Windows Vista also offers a 3D view of the windows themselves that animates as the user cycles through it. The behaviour is very similar to Alt-Tab and is accessed by holding down the Windows key instead of Alt while pressing tab. While this view is visible, windows can be selected and made active by clicking on them with the mouse.

If there is only one window on the system, Windows does not show a selector dialog at all when Alt-Tab is pressed; the key sequence will simply restore or give focus to that window in case it is minimized or not focused.

If you prefer the smaller XP icons over the larger Vista "thumbnail" icons, you can change the functionality by:

* Start → Computer
* Hit the "System Properties" button (on the Toolbar under the File | Edit toolbar)
* Select "Advanced System Settings" (under Tasks grouping in the left-hand column); this gives you "System Properties" dialogue box, the "Advanced Tab" should be displayed.
* Hit the Settings Button under Performance. Uncheck the "Enable Desktop Composition" checkbox (the 3rd checkbox from the top in the Custom list box).
* Hit OK

freelancer Non-Windows functionality
freelancer Macintosh

Similar functionality exists on Mac OS X using Command instead of Alt, and switching between applications rather than windows. The Macintosh switcher has the additional capabilities of pointing at the desired icon with the mouse (also present in Windows Vista and above), and dropping files on applications' icons. Selected application can be hidden or closed using H or Q button without closing the menu. Command-` works similarly to switch between windows within the same application.

In the classic Mac OS, third party extensions (such as LiteSwitch X and Many Tricks Witch) provided this behavior.
freelancer Unix

Unix-like desktop systems such as fvwm, KDE, and GNOME have added a compatible function. On some systems including Sun's CDE and old versions of fvwm, the Alt-Tab key combination is mapped to less sophisticated functionality such as only alternating between two windows, cycling forward or backward in a list of all windows in a fixed order, or opening a task applet in which one has to use arrow keys or the mouse to select a task and then click or push Enter. Some window managers such as WindowLab forego the onscreen window list and simply bring each window to the front in turn as Alt-Tab is pressed.

Not all window managers provide this functionality as a core feature. For example, Blackbox does not; users desiring this behavior can add it by running a helper application such as bbkeys.
freelancer Compiz Fusion

Compiz Fusion (aka Beryl, Compiz) has similar functionality, but displays a preview of the window as well as its icon (Present in Windows Vista and above, with DWM enabled). It also makes use of Alt-Shift-Tab by moving backwards through the displayed programs, and it is possible to activate a Windows Flip 3D alternative using the Windows key and Tab.
freelancer GNOME

Metacity, the GNOME window manager, has similar functionality to versions of Windows released before Vista, but it only displays the outline of the currently selected window on the screen. Windows, on the other hand shows the whole selected window, which helps the user to pick the correct window from multiple windows with a similar title or icon.
freelancer History

The Alt-Tab key combination to switch between windows has been present in all versions of Windows since Windows 1.0. However, there was no visual indication of the list of windows available when switching between windows until Windows 3.1, when this feature was introduced as the 'Fast "Alt+TAB" Switching' checkbox in the Display control panel applet, internally known as "CoolSwitch"[8].

Before CoolSwitch, the Alt-Tab combination was similar to the Alt-ESC combination (which also switched windows), but Alt-ESC redrew each window immediately on each stroke, while Alt-TAB brought the windows to the top but did not redraw them until the Alt key was released.
freelancer Inconsistency

An example of a program that violates the expectation that pressing Alt-Tab one time will switch to the previous application is Adobe Reader 7.0.x. Like newer versions of Microsoft Word it attempts to give a separate icon in the Alt-Tab task menu to each MDI document. However, unlike Word, it brings two items to the front of the list whenever a document is selected using Alt-Tab: first an icon representing the main Reader window and then an icon for the individual document. While in Adobe Reader, pressing Alt-Tab one time selects the second item in the list, which is the icon for the PDF document. Adobe Reader remains the current task when Alt-Tab is released. Thus it is demonstrated that the correct operation of Alt-Tab, like some other aspects of the Windows environment such as the Clipboard chain, depends on individual applications being written correctly.

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From Wikipedia, the free encyclopedia

//<![CDATA[ if (window.showTocToggle) { var tocShowText = "show"; var tocHideText = "hide"; showTocToggle(); } //]]> [*] Principles

[*] Organization

[*] RAID 0

[*] RAID 1

[*] RAID 3, RAID 4

[*] RAID 5

[*] RAID 6

[*] RAID 10

[*] RAID 01

[*] Hardware/Software

[*] Standard levels

[*] Nested (hybrid) RAID

[*] New RAID classification

[*] Non-standard levels

[*] Parity calculation; rebuilding failed drives

[*] RAID is not data backup

[*] Implementations

[*] Operating system based ("software RAID")

[*] Hardware-based

[*] Firmware/driver-based RAID ("FakeRAID")

[*] Network-attached storage

[*] Hot spares

[*] Reliability terms

[*] Problems with RAID

[*] Correlated failures

[*] Atomicity

[*] Write cache reliability

[*] Equipment compatibility

[*] Data recovery in the event of a failed array

[*] Drive error recovery algorithms

[*] Increasing recovery time

[*] Other problems and viruses

[*] History

[*] Non-RAID drive architectures

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[*] Principles