The Computer System

5 functional units of a computer

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 09:41:00 -0700

Input Unit: This is the unit used for sending or transferring data, commands into the

Computer for processing, thereby helping users to communicate with the computer system, it acts as an interface between the user and the system.

Examples of input unit are:

i. keyboard,

ii. joysticks,

iii. scanners,

iv. light pen,

v. electronic tablet

vi. Digitizer. Etc.

Processing Unit: This is the responsible for processing all the various operations that goes on in the system unit. It is referred to as the brain of the computer system, without it the computer will be valueless.

Example of processing unit is the central processing unit (CPU).

The processing unit can be divided into three sections:

i Control Unit

ii Arithmetic and logical unit (ALU)

iii Memory Unit.

The Control Unit: This unit coordinates all the various operations of the input and output units in the system unit precisely the Central Processing Unit (CPU).

Functions of the control unit

i. It directs the sequence of operations,

ii. It interprets the instructions, of a program, in storage unit and produces signals the command circuits to execute the instructions.

iii. It directs the flow of all activities in the computer system.

The arithmetic and logical unit: This unit is responsible for performing all the various Arithmetic operation of addition, subtraction, multiplication, division and relational operations Such as not equal to (¹) greater than (>) less than (< ) greater than or equal to (≥) and logical operation. Etc.

The memory unit: This unit otherwise known to be the main or primary memory (storage). It stores information (i.e. instruction data intermediate and final result of processing) that arrives via the input unit so that this information is made available to the appropriate Quarters for further processing after which they can be presented to the user via the Output unit.

The memory unit divided into two:

i. Random Access Memory (RAM)

ii. Read Only Memory(ROM)

Other versions of ROM are:

· PROM(Programmable Read Only Memory)

· EPROM.(Erasable Programmable Read Only Memory)

Output Unit: This unit displays the result of the processed data for the user

Examples of output unit are:

i. monitor (visual display unit-VDU)

ii. Printers

iii. Card Reader

iv. Magnetic Tape

v. Microfilm etc.

functional unit of computer

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 09:37:00 -0700

Basic Functional units of a Computer

The basic computer system consists of five units:

i Input Unit

ii Control Unit

iii Arithmetic Unit(contained in the CPU, or central processing unit),

iv Memory Unit

v Output Unit

Input Unit: This is the unit used for sending or transferring data, commands into the

Computer for processing, thereby helping users to communicate with the computer system, it acts as an interface between the user and the system.

Examples of input unit are:

i. keyboard,

ii. joysticks,

iii. scanners,

iv. light pen,

v. electronic tablet

vi. Digitizer. Etc.

Example of processing unit is the central processing unit (CPU).

The processing unit can be divided into three sections:

i Control Unit

ii Arithmetic and logical unit (ALU)

iii Memory Unit.

The Control Unit: This unit coordinates all the various operations of the input and output units in the system unit precisely the Central Processing Unit (CPU).

Functions of the control unit

i. It directs the sequence of operations,

ii. It interprets the instructions, of a program, in storage unit and produces signals the command circuits to execute the instructions.

iii. It directs the flow of all activities in the computer system.

The memory unit divided into two:

i. Random Access Memory (RAM)

ii. Read Only Memory(ROM)

Other versions of ROM are:

· PROM(Programmable Read Only Memory)

· EPROM.(Erasable Programmable Read Only Memory)

Output Unit: This unit displays the result of the processed data for the user

Examples of output unit are:

i. monitor (visual display unit-VDU)

ii. Printers

iii. Card Reader

iv. Magnetic Tape

v. Microfilm etc.

what is the importance of an operating system

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 09:36:00 -0700

Operating system: it is a collection of software consisting of control routine that co-ordinate hardware activity. It is a term used to describe a collection of program modules that supervises the operation and use of all system resources to ensure their efficient and judicious management. It is a unit of program which takes over the operation of the computer to the extent of being able to allow a number of .program to be run on the computer with little or no human intervention.

Importance of operating system

1. It moderates the relationship between the computer and its peripherals

2. It helps in the management of files,- copying, deleting, moving of files from one storage location to the other.

3. It encourages the memory for its efficient usage and thus adding the speed of the computer.

4. It manages the activities of the processor in terms of job execution according to the priority of arrival ,of jobs

5. It informs the user of nay hardware or software error

6. It makes communication between the computer and the user or the operator possible.

Types of operating system

i. Single user operating system

ii. Multiple user operating system

Examples of Application Software are:

· Word Processor e.g. Microsoft word, word perfect, Word star etc

· Graphical/ desktop packages e.g. Microsoft publisher, paintbrush, Corel draw, Ms Power point, PageMaker etc.

· Database packages e.g. Dbase iii &iv etc

· Spread sheet packages e.g. Ms Excel, etc

types of micro computer

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 09:32:00 -0700

Types of Micro Computers

Microcomputers can be further divided into different types based on the size of their central processing unit (CPU) and other major and minor components. They are;-

(1) Notebook Micro Computers; - these micro computers are having their sizes just like the size of exercise note books. As a result, they are handy.

(2) Laptop Microcomputers; - these are the microcomputers that can be conveniently operated on the lap. They are bigger in size and slightly heavier than the notebooks. They can perform virtually all the function of the desktop microcomputers, yet very portable like the briefcase size. They can perform complex task anywhere, anytime with ease. They are expensive compare to other microcomputers with larger sizes; this is as a result of high technology with reduction in size.

(3) Desktop Microcomputers: these computers can be placed on flat smooth tables (desk) for convenience and comfort ability when in use. They are bigger than notebooks and laptops. They can also perform various complex operations. Desktop microcomputers are subdivided into their sub-devices/ parts eg. The keyboard, monitor, system unit are all separated from one another having cables used for their connection before use unlike notebooks and laptop where all are permanently joined (connected) together when manufacture.

(4) Minitower Microcomputers: these are recent modification on the system unit, whereby the system unit is made to stand erect on its own and placed beside the monitor unlike desktop which lies flat on tables and monitors placed on it. They also have their parts separately having cables for connection.

(5) Full Tower microcomputer: These computers are closely related to the mini Tower, except that they are a bit higher and wider in physical size than the Mini Tower. All other things are the same as in Mini Tower Microcomputers.

classification of computer by size

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 09:31:00 -0700

There are 3 type of computer in this category; they are:

1. Mainframe Computers: These are very large computers that require extensive space, and they are very expensive to buy and maintain. They are general purpose in nature and have very large computing power, which enable them to be capable of handling multiple simultaneous activities like batch processing, Interactive processing, transaction processing, all other under the control of an operating system that provide for scheduling and control facilities. Their main memory is large and a lot of data and instruction can be stored their.

Their processing speed is high and they can only be used in large organization or institution where very large amount of information are been processed like banks, insurance companies, manufacturing firms, universities, etc. an example is IBM 370.

2 Mini Computers: These are smaller in size than the mainframes but bigger than the micro computers. They are less expensive to mainframes computers; as a result, they are affordable to medium size organizations.

Although, most of them are general purpose in nature, some are still been used for special or dedicated purposes. When compared with mainframes, their processing speed is slower, their main memory smaller and their capability to support secondary storage system are lower but they are larger in the same terms than micro computers. They have the ability to handle complex calculations.

3 Micro Computers); - micro computers are the smallest and the cheapest when compared with mainframes and mini computers. They are otherwise known as personal computers (PC) because they are designed as single user system. Their processing speed is the highest and their central processing units (CPU) consist of microprocessors placed on silicon chips. Present day micro computers are very complex, powerful, rugged, have very large storage capacity and some of them are very portable as we shall discuss the types of micro computers now.

types of computer software

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 08:57:00 -0700

Types Computer systems divide software systems into three major classes: i. System software, ii. Programming software and iii. Application software, although the distinction is arbitrary, and often blurred. • System software helps run the computer hardware and computer system. It includes operating systems, device drivers, diagnostic tools, servers, windowing systems, utilities and more. The purpose of systems software is to insulate the applications programmer as much as possible from the details of the particular computer complex being used, especially memory and other hardware features, and such as accessory devices as communications, printers, readers, displays, keyboards, etc. • Programming software usually provides tools to assist a programmer in writing computer programs and software using different programming languages in a more convenient way. The tools include text editors, compilers, interpreters, linkers, debuggers, and so on. An Integrated development environment (IDE) merges those tools into a software bundle, and a programmer may not need to type multiple commands for compiling, interpreter, debugging, tracing, and etc., because the IDE usually has an advanced graphical user interface, or GUI. • Application software allows end users to accomplish one or more specific (non-computer related) tasks. Typical applications include industrial automation, business software, educational software, medical software, databases, and computer games. Businesses are probably the biggest users of application software, but almost every field of human activity now uses some form of application software.

Importance of operating system

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 08:55:00 -0700

Importance of operating system

1. It moderates the relationship between the computer and its peripherals

2. It helps in the management of files,- copying, deleting, moving of files from one storage location to the other.

3. It encourages the memory for its efficient usage and thus adding the speed of the computer.

4. It manages the activities of the processor in terms of job execution according to the priority of arrival ,of jobs

5. It informs the user of nay hardware or software error

6. It makes communication between the computer and the user or the operator possible.

Types of operating system

i. Single user operating system

ii. Multiple user operating system

Examples of Application Software are:

· Word Processor e.g. Microsoft word, word perfect, Word star etc

· Graphical/ desktop packages e.g. Microsoft publisher, paintbrush, Corel draw, Ms Power point, PageMaker etc.

· Database packages e.g. Dbase iii &iv etc

· Spread sheet packages e.g. Ms Excel, etc

Operating system

noreply@blogger.com (Unknown) — Sun, 31 Jul 2016 08:34:00 -0700

Importance of operating system

1. It moderates the relationship between the computer and its peripherals

2. It helps in the management of files,- copying, deleting, moving of files from one storage location to the other.

3. It encourages the memory for its efficient usage and thus adding the speed of the computer.

4. It manages the activities of the processor in terms of job execution according to the priority of arrival ,of jobs

5. It informs the user of nay hardware or software error

6. It makes communication between the computer and the user or the operator possible.

Types of operating system

i. Single user operating system

ii. Multiple user operating system

Examples of Application Software are:

· Word Processor e.g. Microsoft word, word perfect, Word star etc

· Graphical/ desktop packages e.g. Microsoft publisher, paintbrush, Corel draw, Ms Power point, PageMaker etc.

· Database packages e.g. Dbase iii &iv etc

· Spread sheet packages e.g. Ms Excel, etc

Benefits of Nimble over NetApps

noreply@blogger.com (Unknown) — Wed, 27 Jul 2016 09:32:00 -0700

Faster Performance

Virtually Zero downtime

Less Rackspace

Integrated Data Protection

Offers greater redundancy for stored data;

Enhances reliability

Monitors and analyzes data to identify trends and abnormal operations; sends alerts on critical issues

Creates copies of existing active volumes without needing to copy data

Allows remote troubleshooting, configuration, and problem resolution

Simplifies disaster recovery, including testing failover/failback

Enhances security around storage and reduces risk to data;

Efficiently safeguard stored data

Nimble Protection Manager (NPM); Ensures application-consistent snapshots

Advantages and Disadvantages of computer Network

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:47:00 -0700

Advantages of computer Network
•    Resource sharing
•    Man power is reduced
•    Each workstation on the network can send or receive messages to and fro other workstations on the network.
•    Component evolution can be independent of system evolution and vice versa.

Disadvantages of computer Networks
•    Network hardware, operating system and the software that run on the network can be expensive.
•    There is possibility of purchasing software with incorrect user license
•    The management and control of computer network requires many hours of dedication and service.
•    A network may suffer terribly if the file sever cannot adequately serve the entire request from the users of the network.

Basic Hardware Components

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:46:00 -0700

All networks are made up of basic hardware building blocks to interconnect network nodes, such as
1.    Network Interface Cards (NICs),
2.    Bridges,
3.    Hubs,
4.    Switches, and
5.    Routers.

A network card, network adapter or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network.
A repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation.

Hubs
A hub contains multiple ports. When a packet arrives at one port, it is copied to all the ports of the hub. When the packets are copied, the destination address in the frame does not change to a broadcast address. It does this in a rudimentary way; it simply copies the data to all of the Nodes connected to the hub.

Bridges
A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model.

Switches
Switches are a marketing term that encompasses routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier).

Routers
Routers are the networking device that forward data packets along networks by using headers and forwarding tables to determine the best path to forward the packets that have been integrated with routers to allow multiple home computers to access the Internet.

Types of Computer Networks

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:43:00 -0700

        i.            Personal Area Network (PAN)

A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that may be used in a PAN are printers, fax machines, telephones, PDAs or scanners. The reach of a PAN is typically within about 20-30 feet (approximately 4-6 Meters). PANs can be used for communication among the individual devices (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink).

Personal area networks may be wired with computer buses such as USB and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA and Bluetooth.

     ii.            Local Area Network (LAN)

A network covering a small geographical area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library will have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) connects to the internet. All of the PCs in the library are connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnection devices and eventually connect to the internet. The cables to the servers are on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbps.

   iii.            Campus Area Network (CAN)

A network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.

This term is most often used to discuss the implementation of networks for a contiguous area. For Ethernet based networks in the past, when layer 2 switching (i.e., bridging (networking) was cheaper than routing, campuses were good candidates for layer 2 networks, until they grew to very large size. Today, a campus may use a mixture of routing and bridging. The network elements used, called "campus switches", tend to be optimized to have many Ethernet-family (i.e., IEEE 802.3) interfaces rather than an arbitrary mixture of Ethernet and WAN interfaces.

   iv.            Metropolitan Area Network (MAN)

A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN.

      v.            Wide Area Network (WAN)

A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.

   vi.            Global Area Network (GAN)

Global area networks (GAN) specifications are in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is "handing off" the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial Wireless local area networks (WLAN) [3]. INMARSAT has defined a satellite-based Broadband Global Area Network (BGAN).

IEEE mobility efforts focus on the data link layer and make assumptions about the media. Mobile IP is a network layer technique, developed by the IETF, which is independent of the media type and can run over different media while still keeping the connection.

Computer Network

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:38:00 -0700

Computer network is an interconnection of a group of computers. A computer that controls other computer on the network is called a Server. A computer that is controlled by the server is called Client or Workstation

Network topology

Network Topology signifies the way in which intelligent devices in the network see their logical relations to one another

Computer networks may be classified according to the network topology upon which the network is based, such as

                                i.            Bus network,

                              ii.            Star network,

                            iii.            Ring network,

                            iv.            Mesh network,

                              v.            Star-bus network,

                            vi.            Tree or Hierarchical topology network, etc.
Bus
The simplest topology to understand is the Bus. In a Bus, all the devices on the network are connected to a common cable. Normally, this cable is terminated at either end, and can never be allowed to form a closed loop. Figure One shows an example of a Bus network

Bus

The simplest topology to understand is the Bus. In a Bus, all the devices on the network are connected to a common cable. Normally, this cable is terminated at either end, and can never be allowed to form a closed loop. Figure below shows an example of a Bus network.

Ring

A Ring topology is very similar to the Bus. In a Ring, all the devices on the network are connected to a common cable which loops from machine to machine. After the last machine on the network, the cable then returns to the first device to form a closed loop. Figure below shows an example of a Ring network.

Star

A star topology is completely different from either a Bus or a Ring. In a Star each device has its own cable run connecting the device to a common hub or concentrator. Only one device is permitted to use each port on the hub. Figure below shows an example of a Star network.

Tree

A tree topology can be thought of as being a "Star of Stars" network. In a Tree network, each device is connected to its own port on a concentrator in the same manner as in a Star. However, concentrators are connected together in a hierarchical manner -- i.e. a hub will connect to a port on another hub. Figure below shows a Tree network.

Mesh

A Mesh topology consists of a network where every device on the network is physically connected to every other device on the network. This provides a great deal of performance and reliability, however the complexity and difficulty of creating one increases geometrically as the number of nodes on the network increases. For example, a three or four node mesh network is relatively easy to create, whereas it is impractical to set up a mesh network of 100 nodes -- the number of interconnections would be so ungainly and expensive that it would not be worth the effort. Mesh networks are not used much in local area networks (LANs) but are used in Wide Area Networks (WANs) where reliability is important and the number of sites being connected together is fairly small. Figure below shows an example of a four-node Mesh network.

Types of Computer Networks

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:22:00 -0700

i.    Personal Area Network (PAN)
A personal area network (PAN) is a computer network used for communication among computer devices close to one person. Some examples of devices that may be used in a PAN are printers, fax machines, telephones, PDAs or scanners. The reach of a PAN is typically within about 20-30 feet (approximately 4-6 Meters). PANs can be used for communication among the individual devices (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink).
Personal area networks may be wired with computer buses such as USB and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA and Bluetooth.

ii.    Local Area Network (LAN)
A network covering a small geographical area, like a home, office, or building. Current LANs are most likely to be based on Ethernet technology. For example, a library will have a wired or wireless LAN for users to interconnect local devices (e.g., printers and servers) connects to the internet. All of the PCs in the library are connected by category 5 (Cat5) cable, running the IEEE 802.3 protocol through a system of interconnection devices and eventually connect to the internet. The cables to the servers are on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 Gbps.

iii.    Campus Area Network (CAN)
A network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.
This term is most often used to discuss the implementation of networks for a contiguous area. For Ethernet based networks in the past, when layer 2 switching (i.e., bridging (networking) was cheaper than routing, campuses were good candidates for layer 2 networks, until they grew to very large size. Today, a campus may use a mixture of routing and bridging. The network elements used, called "campus switches", tend to be optimized to have many Ethernet-family (i.e., IEEE 802.3) interfaces rather than an arbitrary mixture of Ethernet and WAN interfaces.

iv.    Metropolitan Area Network (MAN)
A Metropolitan Area Network is a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN.

v.    Wide Area Network (WAN)
A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.

vi.    Global Area Network (GAN)
Global area networks (GAN) specifications are in development by several groups, and there is no common definition. In general, however, a GAN is a model for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is "handing off" the user communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial Wireless local area networks (WLAN) [3]. INMARSAT has defined a satellite-based Broadband Global Area Network (BGAN).
IEEE mobility efforts focus on the data link layer and make assumptions about the media. Mobile IP is a network layer technique, developed by the IETF, which is independent of the media type and can run over different media while still keeping the connection.

Operation

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:16:00 -0700

Computer software has to be "loaded" into the computer's storage (such as a hard drive, memory, or RAM). Once the software is loaded, the computer is able to execute the software. Computers operate by executing the computer program. This involves passing instructions from the application software, through the system software, to the hardware which ultimately receives the instruction as machine code. Each instruction causes the computer to carry out an operation -- moving data, carrying out a computation, or altering the control flow of instructions.
Data movement is typically from one place in memory to another. Sometimes it involves moving data between memories and registers which enable high-speed data access in the CPU. Moving data, especially large amounts of it, can be costly. So, this is sometimes avoided by using "pointers" to data instead. Computations include simple operations such as incrementing the value of a variable data element. More complex computations may involve many operations and data elements together.
Instructions may be performed sequentially, conditionally, or iteratively. Sequential instructions are those operations that are performed one after another. Conditional instructions are performed such that different sets of instructions execute depending on the value(s) of some data. In some languages this is known as an "if" statement. Iterative instructions are performed repetitively and may depend on some data value. This is sometimes called a "loop." Often, one instruction may "call" another set of instructions that are defined in some other program or module. When more than one computer processor is used, instructions may be executed simultaneously.
A simple example of the way software operates is what happens when a user selects an entry such as "Copy" from a menu. In this case, a conditional instruction is executed to copy text from data in a 'document' area residing in memory, perhaps to an intermediate storage area known as a 'clipboard' data area. If a different menu entry such as "Paste" is chosen, the software may execute the instructions to copy the text from the clipboard data area to a specific location in the same or another document in memory.
Depending on the application, even the example above could become complicated. The field of software engineering endeavors to manage the complexity of how software operates. This is especially true for software that operates in the context of a large or powerful computer system.
Currently, almost the only limitation on the use of computer software in applications is the ingenuity of the designer/programmer. Consequently, large areas of activities (such as playing grand master level chess) formerly assumed to be incapable of software simulation are now routinely programmed. The only area that has so far proved reasonably secure from software simulation is the realm of human art— especially, pleasing music and literature.

License
Software license gives the user the right to use the software in the licensed environment; some software comes with the license when purchased off the shelf, or an OEM license when bundled with hardware. Other software comes with a free software license, granting the recipient the rights to modify and redistribute the software. Software can also be in the form of freeware or shareware. See also License Management.

Patents
The issue of software patents is controversial. Some believe that they hinder software development, while others argue that software patents provide an important incentive to spur software innovation. See software patent debate.

Ethics and rights for software users
Being a new part of society, the idea of what rights users of software should have is not very developed. Some, such as the free software community, believe that software users should be free to modify and redistribute the software they use. They argue that these rights are necessary so that each individual can control their computer, and so that everyone can cooperate, if they choose, to work together as a community and control the direction that software progresses in. Others believe that software authors should have the power to say what rights the user will get.

Program and library

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:14:00 -0700

A program may not be sufficiently complete for execution by a computer. In particular, it may require additional software from a software library in order to be complete. Such a library may include software components used by stand-alone programs, but which cannot work on their own. Thus, programs may include standard routines that are common to many programs, extracted from these libraries. Libraries may also include 'stand-alone' programs which are activated by some computer event and/or perform some function (e.g., of computer 'housekeeping') but do not return data to their calling program. Libraries may be called by one to many other programs; programs may call zero to many other programs.

Three layers
Users often see things differently than programmers. People who use modern general purpose computers (as opposed to embedded systems, analog computers, supercomputers, etc.) usually see three layers of software performing a variety of tasks:
1.    platform,
2.    application, and
3.    user software.

1.    Platform software
Platform includes the firmware, device drivers, an operating system, and typically a graphical user interface which, in total, allow a user to interact with the computer and its peripherals (associated equipment). Platform software often comes bundled with the computer. On a PC you will usually have the ability to change the platform software.
2.    Application software
Application software or Applications are what most people think of when they think of software. Typical examples include office suites and video games. Application software is often purchased separately from computer hardware. Sometimes applications are bundled with the computer, but that does not change the fact that they run as independent applications. Applications are almost always independent programs from the operating system, though they are often tailored for specific platforms. Most users think of compilers, databases, and other "system software" as applications.
3.    User-written software
User software tailors systems to meet the user’s specific needs. User software includes spreadsheet templates, word processor macros, scientific simulations, and scripts for graphics and animations. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is. Depending on how competently the user-written software has been integrated into purchased application packages, many users may not be aware of the distinction between the purchased packages, and what has been added by fellow co-workers.

Computer Software

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:13:00 -0700

Computer software is a general term used to describe a collection of computer programs, procedures and documentation that perform some task on a computer system. The term includes application software such as word processors which perform productive tasks for users, system software such as operating systems, which interface with hardware to provide the necessary services for application software, and middleware which controls and co-ordinates distributed systems.

Terminology
The term "software" is sometimes used in a broader context to describe any electronic media content which embodies expressions of ideas such as film, tapes, records, etc.

Relationship to computer hardware
Computer software is so called to contrast with computer hardware, which encompasses the physical interconnections and devices required to store and execute (or run) the software. In computers, software is loaded into RAM and executed in the central processing unit. At the lowest level, software consists of a machine language specific to an individual processor. A machine language consists of groups of binary values signifying processor instructions (object code), which change the state of the computer from its preceding state. Software is an ordered sequence of instructions for changing the state of the computer hardware in a particular sequence. It is usually written in high-level programming languages that are easier and more efficient for humans to use (closer to natural language) than machine language. High-level languages are compiled or interpreted into machine language object code. Software may also be written in an assembly language, essentially, a mnemonic representation of a machine language using a natural language alphabet. Assembly language must be assembled into object code via an assembler.
The term "software" was first used in this sense by John W. Tukey in 1958.[3] In computer science and software engineering, computer software is all computer programs. The theory that is the basis for most modern software was first proposed by Alan Turing in his 1935 essay Computable numbers with an application to the Entscheidungsproblem.

Types
Computer systems divide software systems into three major classes:
i.    System software,
ii.    Programming software and
iii.    Application software, although the distinction is arbitrary, and often blurred.
•    System software helps run the computer hardware and computer system. It includes operating systems, device drivers, diagnostic tools, servers, windowing systems, utilities and more. The purpose of systems software is to insulate the applications programmer as much as possible from the details of the particular computer complex being used, especially memory and other hardware features, and such as accessory devices as communications, printers, readers, displays, keyboards, etc.
•    Programming software usually provides tools to assist a programmer in writing computer programs and software using different programming languages in a more convenient way. The tools include text editors, compilers, interpreters, linkers, debuggers, and so on. An Integrated development environment (IDE) merges those tools into a software bundle, and a programmer may not need to type multiple commands for compiling, interpreter, debugging, tracing, and etc., because the IDE usually has an advanced graphical user interface, or GUI.
•    Application software allows end users to accomplish one or more specific (non-computer related) tasks. Typical applications include industrial automation, business software, educational software, medical software, databases, and computer games. Businesses are probably the biggest users of application software, but almost every field of human activity now uses some form of application software.

Application of computers

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:09:00 -0700

The usefulness of computer has now become part of humanity. It is only better imagined what life would have been without them

Computers are capable of helping people to conduct their lives, meaningful, efficient and enjoyable ways:

a) The computer can bused efficiently to produce typewritten copiers of letters, memos, and other form personnel correspondence.

b) Computer assists in education process by bringing education into the home. They provide lesson for leaning how to use a computer.

c) Computers are being used as educational delivery system. That is computers are programmed to deliver education content to individual students

d) Computers are one of the main tools in putting together data and histories for individual patients and in making these records available to doctors.

e) Application of computer in health care

Computers have played such important part in the growth and improvement of healthcare that the use of computers in medicine has become a medical specialist in itself. Computer can be used in diagnosing illness and administering of treatments.

f) Computers are important tool in research work.

g) Computers systems are used in carrying out engineering research on rocket ting and space travel.

h) Computers are used to simulate data for laboratory test in the modeling of machine and equipment and the result is viewed on the monitor before actual manufacturing.

i) Computer can be used in the Banks to keep record of customers account.

Computer Memory

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:09:00 -0700

Computer memory is the medium of storage for the computer system. The computer memory stores data, information, programs in itself for use.

These are 2 main types of computer memory. They are:-

i. Internal/Main/Primary memory

ii. External/Auxiliary/Secondary Memory

Internal Memory: this memory is considered to be part of the Central Processing Unit (CPU). It stores data and information that are needed for the immediate execution and programs currently run are held in it. Generally, the large capacity of the internal memory makes a computer to be extra powerful by being able to accommodate and run multiple programs during simultaneous execution and assessment. Also, it increases the speed of program execution.

The internal memory is divided into two parts, they are;-

- random access memory (RAM)

- read only memory (ROM)

(1) Random Access Memory;- form the larger part of the internal memory inmost computers. This is the part that users have access to because it is ion this part that currently run programs are been held temporally until they are transferred (saved) into the external memory, they are liable to get lost except there is provision for backup facility on the computer.

(2) Read Only Memory;- is a permanent (non volatile) memory that holds important frequently used programs which are made available for each time they are needed. Programs stored inside the ROM cannot be altered by the user(s) by any means, thereby rendering security (protection) for such programs (because users do not have access to it (ROM) rather than making use of it when required). For example, the operating system is kept in the ROM.

Difference between RAM and ROM

s/n	Random Access Memory	Read Only Memory
1	Information can be written on a RAM	Information cannot be written on a ROM
2 3	Information can be retrieve from a RAM RAM has no fixed size	Information can not be retrieve from a ROM ROM has a fixed size
4 5	In formation are not permanent Application programs are processed through the RAM	Information are permanent in ROM ROM contains system programs, which is responsible for booting processing of the computer system as well as the configuration of the system.

The External Memory: There are some programs which need not to be kept in the internal memory because they are not often needed for use, although the internal memory cannot even contain them since some of them are very are large. This set of program are stored in the external memory (but will be loaded in the internal memory when needed for execution) which is not part of the CPU but different on its own as component though it is connected on-line to the CPU. It is permanent storage medium; therefore stands as effective backup in case of any damage or loss of data in the RAM of the internal memory. It has larger memory capacity than the internal memory.

Common examples of external devices are:-

i. Magnetic disk,

ii. Magnetic tapes,

iii. Floppy disk(diskette),

iv. Hard disk,

v. CD-ROMs, etc.

The memory capacities (size) of these devices are measured in the unit known as byte. A byte refers to the number of bit required to represent each character on the computer and it’s generally equal to eight bits i.e. 1byte=8bits (bits are in 0s and 1s) by extension we can say I kilobyte=1000bytes, though in the real sense of it, it 1024 bytes that makes 1kb

One Kilobyte or 1kb = 1000bytes

One Megabyte or 1Mb=1000000bytes

One Gigabyte or 1 GB = 1000, 000,000bytes

Different between Internal and External Memory

S/N	Internal Memory\|	External Memory\|
1 2 3 4 5	It is very fast in its operation It is very expensive It is within the computer Central Processing Unit(CPU) It is very volatile(Temporal) It is limited in capacity for storage	It is slow its operation It is not expensive It is not within the Central Processing Unit(CPU) It is not volatile but permanent It has unlimited for storage

Components of the Computer System

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:07:00 -0700

The computer system is made of three (3) major components,

1. Hardware,

2. Software and

3. Human ware.

1. Hardware: This refers to the physical parts of the computer which can be seen, touched and moved from one place to another. All these parts containing the main parts and the peripheral devices have been divided into four main groups. They are:-

i) Input devices

ii) Processing device

iii) Output devices

iv) Storage devices

Input Devices: - these are the computer parts used for sending (transferring) data, information, commands, etc into the computer system. Examples are the keyboard, Mouse, Light pen, Graphic, scanner, Electronic tablet, Joystick, etc.

Processing Device: - this is the part of the computer that processes all the activities (operation) regarding the computer system. It is known as the engine of the computer.

Output Devices: - these are the computer parts that are responsible for displaying or giving out result (outcome of the activities performed in the computer. Examples are the Monitor, Printer, Plotter, etc.

Note:- Information displayed on the Monitor are known as the Soft Copy while the ones printed out on papers by the printer are called/ known as Hard Copy of the information(Information here refer to various forms of document)

Storage Devices: - These are the part of the computer that helps to store data or information in the computer for subsequent or future references. Examples of these are the Hard disk, Floppy disk popularly known as the Diskette, cartridge, CD-ROM (Compact Disk-Read Only Memory)

2. Software: This refers to the set of programs that enables the computer to work. Soft wares are stored inside the computer memory.

There are different types of software, they are:-

i. System Software and

ii. Application Software

An example of System Software is the operating system such as Windows XP.

Importance of operating system

1. It moderates the relationship between the computer and its peripherals

2. It helps in the management of files,- copying, deleting, moving of files from one storage location to the other.

3. It encourages the memory for its efficient usage and thus adding the speed of the computer.

4. It manages the activities of the processor in terms of job execution according to the priority of arrival ,of jobs

5. It informs the user of nay hardware or software error

6. It makes communication between the computer and the user or the operator possible.

Types of operating system

i. Single user operating system

ii. Multiple user operating system

Examples of Application Software are:

· Word Processor e.g. Microsoft word, word perfect, Word star etc

· Graphical/ desktop packages e.g. Microsoft publisher, paintbrush, Corel draw, Ms Power point, PageMaker etc.

· Database packages e.g. Dbase iii &iv etc

· Spread sheet packages e.g. Ms Excel, etc

3. Human ware

This refers to the set of people working in connection with the computer. Examples are

· Computer operators

· Computer programmers

· Computer Engineers

· Computer Analysts

Classification of Computer System

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 18:05:00 -0700

Computers have been classified into five (5) different categories viz;

- Classification by generation (this have been discussed un the previous notes)

- Classification by type or mode of processing

- Classification by size

- Classification by function

- Classification by programmability

Classification of Computer by type of Mode of Processing

There are three types of computer under this category. They are:

1.Digital Computers: These are computer designed to processed data in discrete numerical form which are represented by discrete signal using binary code, numbers, letters, and symbols are represented by codes based on the binary number system consisting of two digits .i.e. 1,0 the digital computer must convert all data to binary form. Generally, results from digital computer are more than the results from analog computers. They are used for counting and calculating numbers. Examples are calculator, adding machine, counting machine, etc.

2. Analogue Computers: These are computers that measure the continuous physical magnitude or electrical states. For example pressure, temperature, voltage, volume, etc.

For instance a petrol pump at the filling station uses an analog device to measure the quantity of petrol to the nearest Naira/Kobo and the quantity of the pumped fuel to the nearest one tenth of a liter. A speedometer in a vehicle is another example of analog computer

Analog computers are used for scientific, engineering and process control purposes. Since they deal with quantities that are continuously varying in nature, they give only approximate result i.e. Not accurate results as in digital computer. Other examples are the thermometer, volume control of a TV set meter.etc.

3. Hybrid Computers: These are computers that combine the features of digital and Analog computers together. They can be used for both counting and measuring. In fact, they are very useful in the control of manufacturing and processing.

Classification of Computer by Size

There are 3 type of computer in this category; they are:

Types of Micro Computers

Microcomputers can be further divided into different types based on the size of their central processing unit (CPU) and other major and minor components. They are;-

(1) Notebook Micro Computers; - these micro computers are having their sizes just like the size of exercise note books. As a result, they are handy.

Classification of Computer by Function

There are two (2) types of computer under this category. They are

(1) General Purpose Computers: - These are multipurpose Computers capable of solving a wide range of problems (task). They can be used in and for various aspects like drawing, calculating, designing, typing, multi-media functions, playing games. Etc. Examples are the Desktop computers, Laptop, Mini Tower computer, etc

(2) Special Computers: these are dedicated computers designed solely for the purpose for solving a particular problem. Examples are the road Traffic Light control, calculators Robots (Robotics), Counting Machines, etc.

Classification of Computer by Programmability

There are two (2) types of Computer under this class, they are:-

i. Programmable Computers and

ii. Non Programmable Computers

(a) Programmable Computers: - These are computer designed to accept different programs from users to solve problems. Computer that are generally suited to carry out such programming task are programmable computer. Examples are the Micro Computer, Mainframe Computers. Etc.

(b) Non Programmable Computers:- These are computers designed to tackle a particular set of tasks, therefore can not accept any other program from any user apart from what it is meant for. They are similar to the special/dedicated purpose Computers. Examples are the Temperature Thermometer, X-ray Machine, Vehicle Speedometer, Wind Vane Hydrometer, Hygrometer, etc.

Characteristics of a Computer System

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 17:59:00 -0700

1. Accuracy: computers operate at a very high degree of accuracy. It does not become exhausted easily to the extent of making mistakes.

2. Speed: computer is generally known for its speed. The speed of computer is measure in millions of instruction per seconds and it increases progressively as the computer develops.

3. Reliability; the computer responds to the instruction keyed into it without any alteration, as a result of this, it gives no room for doubt over out output. Therefore, the operator relies on it for effectiveness. Example include a program computer device to ring alarm to alert workers of any emergency, a programmed entry and exit door used in big companies and supermarkets, offices, etc.

4 Versatility; it fits into different fields of human endeavor ranging from business, education, technology, engineering, law, commerce, agriculture, medicine, sports.etc it can perform different types of tasks provided such tasks can be stated in logical way for the computer to execute.

5. Large Storage Capacity: vast quantities of data stored in paper files would become extremely bulky and require substantial storage space. Furthermore, the job of manually extracting data from such files would become increasingly tedious and time consuming as the size of the files increases. But with the computer, data can be stored electronically in considerable less space, and retrieve in a fraction of the time needed by the manual method. The ability of the computer to store, retrieve and process data, all without human intervention gives it power and appeal over that of human.

So, while human can perform the same function as the computer, the difference and major benefits is that the computer can reliably execute millions of instructions in a second and stored the result in an almost unlimited memory.

6. Programmability: The computer can be programmed to do all forms of activities of man. Programming in computer means the act of writing computers programs and this involves the use of special set of characters, signs, symbols, to supply instruction to the computer for execution towards achieving specific tasks (motives). This opportunity gave room for the computer to be a versatile system.

The Computer System

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 17:58:00 -0700

The Computer System

A Computer is an electronic device that accepts data in form of input through an input device process the data and yield results (output).

In order word computer can be defined as an electronic device that process data to yield useful information.

Basic Functional units of a Computer

The basic computer system consists of five units:

i Input Unit

ii Control Unit

iii Arithmetic Unit(contained in the CPU, or central processing unit),

iv Memory Unit

v Output Unit

This organization of the functional parts is called the architecture of the computer.

Fig 1.1 General Organization of a computer

Input Unit: This is the unit used for sending or transferring data, commands into the

Computer for processing, thereby helping users to communicate with the computer system, it acts as an interface between the user and the system.

Examples of input unit are:

i. keyboard,

ii. joysticks,

iii. scanners,

iv. light pen,

v. electronic tablet

vi. Digitizer. Etc.

Example of processing unit is the central processing unit (CPU).

The processing unit can be divided into three sections:

i Control Unit

ii Arithmetic and logical unit (ALU)

iii Memory Unit.

The Control Unit: This unit coordinates all the various operations of the input and output units in the system unit precisely the Central Processing Unit (CPU).

Functions of the control unit

i. It directs the sequence of operations,

ii. It interprets the instructions, of a program, in storage unit and produces signals the command circuits to execute the instructions.

iii. It directs the flow of all activities in the computer system.

The memory unit divided into two:

i. Random Access Memory (RAM)

ii. Read Only Memory(ROM)

Other versions of ROM are:

· PROM(Programmable Read Only Memory)

· EPROM.(Erasable Programmable Read Only Memory)

Output Unit: This unit displays the result of the processed data for the user

Examples of output unit are:

i. monitor (visual display unit-VDU)

ii. Printers

iii. Card Reader

iv. Magnetic Tape

v. Microfilm etc.

The Five Generations of Computers

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 17:41:00 -0700

The history of computer development is often referred to in reference to the different generations of computing devices. Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate, resulting in increasingly smaller, cheaper, more powerful and more efficient and reliable devices. Read about each generation and the developments that led to the current devices that we use today.

First Generation - 1940-1956: Vacuum Tubes
The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions. First generation computers relied on machine language to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.

The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.

Second Generation - 1956-1963: Transistors
Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 50s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.

Second-generation computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions of COBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.

The first computers of this generation were developed for the atomic energy industry.

Third Generation - 1964-1971: Integrated Circuits
The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.

Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

Fourth Generation - 1971-Present: Microprocessors
The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer - from the central processing unit and memory to input/output controls - on a single chip.

In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.

As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handheld devices.

Fifth Generation - Present and Beyond: Artificial Intelligence
Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.

Early Computing Machines and Inventors

noreply@blogger.com (Unknown) — Fri, 22 Jul 2016 17:41:00 -0700

The real beginnings of computers as we know them today lay with an English mathematics professor, Charles Babbage (1791-1871). Frustrated at the many errors he found while examining calculations for the Royal Astronomical Society, Babbage declared, "I wish to God these calculations had been performed by steam!" With those words, the automation of computers had begun.

By 1812, Babbage noticed a natural harmony between machines and mathematics: machines were best at performing tasks repeatedly without mistake; while mathematics, particularly the production of mathematic tables, often required the simple repetition of steps. The problem centered on applying the ability of machines to the needs of mathematics. Babbage's first attempt at solving this problem was in 1822 when he proposed a machine to perform differential equations, called a Difference Engine. Powered by steam and large as a locomotive, the machine would have a stored program and could perform calculations and print the results automatically. After working on the Difference Engine for 10 years, Babbage was suddenly inspired to begin work on the first general-purpose computer, which he called the Analytical Engine. Babbage's assistant, Augusta Ada King, Countess of Lovelace (1815-1842) and daughter of English poet Lord Byron, was instrumental in the machine's design. One of the few people who understood the Engine's design as well as Babbage, she helped revise plans, secure funding from the British government, and communicate the specifics of the Analytical Engine to the public. Also, Lady Lovelace's fine understanding of the machine allowed her to create the instruction routines to be fed into the computer, making her the first female computer programmer. In the 1980's, the U.S. Defense Department named a programming language ADA in her honor.

Babbage's steam-powered Engine, although ultimately never constructed, may seem primitive by today's standards. However, it outlined the basic elements of a modern general purpose computer and was a breakthrough concept. Consisting of over 50,000 components, the basic design of the Analytical Engine included input devices in the form of perforated cards containing operating instructions and a "store" for memory of 1,000 numbers of up to 50 decimal digits long. It also contained a "mill" with a control unit that allowed processing instructions in any sequence, and output devices to produce printed results. Babbage borrowed the idea of punch cards to encode the machine's instructions from the Jacquard loom. The loom, produced in 1820 and named after its inventor, Joseph-Marie Jacquard, used punched boards that controlled the patterns to be woven.