Dushmanta Nath

HSLC RESULT 2011 [SEBA]

2011-05-27T00:17:00.000-07:00

HSLC RESULT 2011 [SEBA]

2011-04-23T14:06:00.001-07:00

My Blog

2011-04-23T12:53:00.000-07:00

IT-314 MIS (Practicals)

2011-04-18T14:51:00.000-07:00

http://www.slideshare.net/dushmanta/it314-mis-practicals/download

Linux Operating System Notes for IT 6th sem

2011-04-17T03:56:00.000-07:00

Linux Operating System Notes for IT 6th sem

Q: What is Linux?
Answer:

Linux is an operating system. It is the software on a computer that enables applications and the computer operator to access the devices on the computer to perform desired functions. The operating system relays instructions from an application to, for instance, the computer's processor. The processor performs the instructed task, then sends the results back to the application via the operating system.
Linux is a Unix-like operating system that was designed to provide personal computer users a free or very low-cost operating system comparable to traditional and usually more expensive Unix systems. Linux has a reputation as a very efficient and fast-performing system. Linux's kernel was developed by Linus Torvalds at the University of Helsinki in Finland. To complete the operating system, Torvalds and other team members made use of system components developed by members of the Free Software Foundation for the GNU Project.

Q: How Linux is Different From Other Operating System?
Answer:

Linux is distinguished from many popular operating systems in three important ways.
•   Linux is a cross-platform operating system that runs on many computer models. In comparison, Windows 95 and Windows 98 run only on CPUs having the Intel architecture. Windows NT runs only on CPUs having the Intel architecture or the DEC Alpha.

•   Linux is free, in two senses. First, we may pay nothing to obtain and use Linux. On the other hand, you may choose to purchase Linux from a vendor who bundles Linux with special documentation or applications, or who provides technical support. Linux is free or nearly free in an economic sense. Second, and more important, Linux and many Linux applications are                                             distributed in source form. This makes it possible for us and others to modify or   improve them.We are not free to do   this with most operating systems, which are   distributed in binary form.

•   Linux has attractive features and performance. Free access to Linux source code lets programmers around the world implement new features, and tweak Linux to improve its performance and reliability. The best of these features and tweaks are incorporated in the standard Linux kernel or made available as kernel patches or applications.

Q: What is Shell ?
Answer:

The command interpreter is the interface between the user and the operating system, hence the name "shell".

The shell therefore acts as an intermediary between the operating system and the user thanks to command lines that are entered by the latter. Its role consists in reading the command line, interpreting its meaning, carry out the command, and then return the result via the outputs.
The shell is an executable file responsible for interpreting the commands, transmitting them to the system, and returning the result. Ther are several shells, the most common being sh (called "Bourne shell"), bash ("Bourne again shell"), csh ("C Shell"), Tcsh ("Tenex C shell"), ksh ("Korn shell"),and zsh ("Zero shell"). Their name generally matches the name of the executable.
Linux Is Portable:

A portable operating system is one that can run on many different machines. More than 95 percent of the Linux operating system is written in the C programming language, and C is portable because it is written in a higher-level, machine-independent language. It can be adapted (ported) to different machines and can meet special requirements. Therefore Linux is portable

Q: What are the features of Linux ?
Answer:

Linux has the following features as an outstanding operating system which is strong in security and networking.

• Multitasking: Several programs can run at the same time.

•Multiuser: Several users can logon to the same machine at the same time There is no need to have separate user licenses.

• Multiplatform: Linux runs on many different CPUs, that means it supports multiprocessor machine.

• Multithreading: Linux has native kernel support for multiple independent threads of control within a single process memory space.

•Crash proof: Linux has memory protection between processes, so that one program can't bring the whole system down.

•Demand loads executables: Linux only reads from those parts of a program that are actually used on the disk.

•Shared copy-on-write pages among executables: This means that multiple processes can use the same memory to run in. When one tries to write to that memory, that page is copied somewhere else. Copy-on-write has two benefits: increasing speed and decreasing memory use.

• Free and Open source code for all: All source code of Linux is available,including the whole kernel and all drivers, the development tools and all user programs; also, all of it is freely distributable.

•Linux has a unified memory pool for user programs and disk cache, so that all free memory can be used for caching, and the cache can be reduced when running large programs.

• Linux is mostly compatible with POSIX, System V, and BSD at the source level.

• Linux has CD-ROM file system which reads all standard formats of CD-ROMs.

• Linux performs well with TCP/IP networking, including ftp, telnet, NFS, etc.

Q: What are standard input and standard output?
Answer:

Most Linux commands read input, such as a file or another attribute for the command, and write output. By default, input is being given with the keyboard, and output is displayed on our screen. Our keyboard is our "standard input" (stdin) device, and the screen or a particular terminal window is the "standard output"
(stdout) device.

Q: What is vim editor?
Answer:

Vim is a highly configurable text editor built to enable efficient text editing..It is an improved version of the vi editor distributed with most UNIX system. Vim is free and open source software. Vim editor consist of many features designed to be helpful in editing program source code. Vim is a cross-platform supporting many other platforms. Lastly Vim is the most popular editor.

Q: What are the three modes of vi editor?
Answer:

The vi editor has three modes, command mode, insert mode and command line mode.
1.   Command mode: Letters or sequences of letters interactively command vi. Commands are case sensitive. The ESC key can end a command.
2.   Insert mode: Text is inserted. The ESC key ends insert mode and returns us to command mode. One can enter insert mode with the "i" (insert), "a" (insert after), "A" (insert at end of line), "o" (open new line after current line) or "O" (Open line above current line) commands.
3.   Command line mode: One enters this mode by typing ":" which puts the command line entry at the foot of the screen.

Q: What are the features of vim?
Answer:

   One extremely convenient feature of vim is its ability to fold text. With this feature, we can make parts of a text file disappear, without actually removing it.
   Another neat feature here is that if we make changes to the fold and add or remove text, vim still remembers the start and end markers and will fold it accordingly.
   Another feature on vim is its abbreviation feature. With it, we can create abbreviations for text. By typing this in command mode:
:abbr ap Apache Web Server.

Q: How Does The Linux File System Work?
Answer:

In Linux, everything is a file. In addition to data and executable files, Linux treats directories and even the various components of your computer as files. When Linux is installed, a file system is carved out of a chunk of hard disk and formatted so that Linux can use it. A hierarchical (treelike) structure for storing files imposes some order on the file system to help both you and Linux find needed files.
There are two ways to manipulate the linux files: using the command line and the Midnight Commander.
We will be creating, deleting, copying, renaming, listing, linking, and protecting the files like a pro. Also we can wipe out the entire file system without really trying.

Q: How Do Linux File Directories Work?
Answer:

A Linux directory is a special file that acts as a container for other files and even other directories. You can create directories to hold groups of related files as an alternative to keeping all your files in one huge directory. A Linux file system is like a filing cabinet with a bunch of folders, each of which can contain subfolders and files.
Important file directories that work with Linux are explain below-
/bin: Contains the Linux system commands and programs (also called binaries
/dev: Contains special device files that correspond to hardware components.
/etc: Contains configuration files for Linux and other installed software
/home: Contains the home directories (personal storage) for each user on the system
/sbin: Contains more Linux binaries (special utilities not for general users).
/root: The home directory for the root user; not to be confused with /. Some Linux systems use /home/root instead of /root
/usr: Contains system programs and other files for general users such as games, online help, and documentation. By convention, a user should not put personal files in this directory.

Q: How can you move a cursor?
Answer:

A single function is provided for moving the cursor, with an additional command for controlling where curses leaves the cursor after screen updates. The move function simply moves the logical cursor position to the specified location. Calling move function won’t cause the physical cursor to move. It only changes the location on the logical screen.
             The leaveok function sets a flag that controls where curses leaves the physical cursor. By default, the flag is false, and the hardware cursor is left in the same position on the screen as the logical cursor. If the flag is set to true, the hardware cursor may be left randomly, anywhere on the screen.

Q: Write a short note on Text Editor.
Answer:

Text editors are similar to word processors, providing various features for writing documents. Several text editors are available on Linux.
Vi:
Vi is often the default editor that pops up when we are ready to write an e-mail message or when we are posting a News message. Vi is complicated and seems difficult to learn at first. However, it is often the default for Unix and Linux systems
Pico:
Pico is a simple text editor that provides straight-forward options and easy-to-use commands. However, Pico is not very good when manipulating certain types of files such as making changes to .cgi files etc.
Emacs:
Emacs is another editor available in UNIX. Like vi, emacs is a screen editor. Unlike vi, emacs is not an insertion mode editor, meaning that any character typed in emacs is automatically inserted into the file, unless it includes a command prefix.

Q: What is Emacs Editor?
Answer:

Emacs is another editor available in UNIX. Like vi, emacs is a screen editor. Unlike vi, emacs is not an insertion mode editor, meaning that any character typed in emacs is automatically inserted into the file, unless it includes a command prefix

Q: What is UNIX?
Answer:

UNIX is a powerful computer operating system. The UNIX operating system was developed at Bell Laboratories in 1969. UNIX operating systems are widely used in servers, workstations, and mobile devices. It is very popular among the scientific, engineering, and academic communities due to its multi-user and multi-tasking environment, flexibility and portability, electronic mail and networking capabilities, and the numerous programming, text processing and scientific utilities available. UNIX systems are characterized by various concepts:
   The use of plain text for storing data;
   A hierarchical file system;
   The use of a large number of software tools;
   Small programs that can be strung together through a command line interpreter using pipes.

Q: What are the advantages of UNIX operating system?
Answer:

The advantages of UNIX operating system are -
   UNIX is flexible and can be installed on many different types of machines.
   UNIX has greater built-in security.
   UNIX is the leader in serving the Web.
   UNIX is free or inexpensive open-source operating systems.
   UNIX is a powerfully unified file system.

Q: Define Header files and Library files.
Answer:

Header files: A header file is a file containing C declarations and macro definitions to be shared between several source files. Some programming languages most famously C, C++, and Objective-C use header files. Header files commonly contain forward declarations of classes, subroutines, variables, and other identifiers.
Library files: Libraries are collections of precompiled function that have been written to be reusable. They consist of sets of related functions to perform a common task. A library file name always starts with lib. Examples include libraries of screen-handling functions and database access routines.

Q: Define Static library and Shared library.
Answer:

Static Library: A static library or statically-linked library is a set of routines, external functions and variables which are resolved in a caller at compile-time. Static libraries are merged with other static libraries. Static libraries can be easily created in C or in C++.
Shared Library: Like an archive library, a shared library contains object code. It covers at least two different concepts. First, it is the sharing of code located on disk by unrelated programs. The second concept is the sharing of code in memory, when programs execute the same physical page of RAM, mapped into different address spaces.

Q: What is Pipes?
Answer:

A very useful Linux feature is named pipes which enable different processes to communicate. A pipe is a technique for passing information from one program process to another. This allows tools quite narrow in their function to be combined in complex ways. A simple example of using a pipe is the command:
Is | grep x

Q: What is /proc file system?
Answer:

The /proc file system is a direct reflection of the system kept in memory and represented in a hierarchal manner. The effort of the /proc file system is to provide an easy way to view kernel and information about currently running processes. As a result, some commands read /proc directly to get information about the state of the system. The premise behind /proc is to provide such information in a readable manner instead of having to invoke difficult to understand system calls.

Q: What /proc file system can do for an Administrator?
Answer:

The /proc file system can be used for system related tasks such as:
•   Viewing Statistical Information.
•   Finding out Hardware Information.
•   Modifying Runtime Parameters.
•   Viewing and Modifying Network and Host Parameters.
•   Memory and Performance Information.

Q: What is Pathname Expansion or Filename Generation?
Answer:
Pathname expansion is also called filename generation is the process of interpreting ambiguous file references and substituting the appropriate list of filenames. The base syntax for the pathname expansion is the pattern matching syntax.

Q: What is the Bourne shell? Write the features of the Bourne shell.
Answer:

The Bourne shell is considered the primary shell in scripts. All UNIX systems have it, first of all. Second, the shell is small and fast. It doesn't have the interactive features of the C shell. Many consider the Bourne shell to be the best shell for writing portable UNIX scripts.
The Bourne shell, or sh, was the default Unix shell of Unix Version 7. Bourne shell scripts can typically be run with bash or dash on GNU/Linux or other Unix-like systems. The binary program of the Bourne shell or a compatible program is located at /bin/sh on most Unix systems, and is still the default shell.
Features of the Bourne shell include:
•   Scripts can be invoked as commands by using their filename.
•   May be used interactively or non-interactively.
•   Allow both synchronous and asynchronous execution of commands.
•   Supports input and output redirection and pipelines.
•   Provides a set of built-in commands.
•   Provides flow control constructs, quotation facilities, and functions.
•   Type less variables.
•   Provides local and global variable scope.
•   Scripts do not require compilation before execution.
•   Does not have a go to facility, so code restructuring may be necessary.

Q: What is Bash?
Answer:

Bash is the shell, or command language interpreter, for the GNU operating system. The name is an acronym for the ‘Bourne-Again Shell’.
Bash is largely compatible with sh. It is intended to be a conformant implementation of the ieee posix Shell and Tools portion of the ieee posix specification It offers functional improvements over sh for both interactive and programming use.
Bash is the default shell. Bash is quite portable. It currently runs on nearly every version of UNIX.
Q: Explain shell basics?
Answer:
The basic actions of the shell are simple. It reads a line. This is either from a file, a script, or from a user.
   First, meta-characters are "handled."
   Second, the name of the executable is found.
   Third, the arguments are passed to the program.
   Fourth, the file redirection is setup.
   Lastly, the program is executed.

Q: Define Parameters and variables.
Answer:
A parameter is an entity that stores values. It can be a name, a number, or one of the special characters. A parameter is set if it has been assigned a value. The null string is a valid value.
A variable has a value and zero or more attributes. Attributes are assigned using the declare builtin command. Once a variable is set, it may be unset only by using the unset builtin command.
A variable may be assigned to by a statement of the form
     name=[value]

Q: Define Shell function.
Answer:
Shell functions are a way to group commands for later execution using a single name for the group. They are executed just like a "regular" command. When the name of a shell function is used as a simple command name, the list of commands associated with that function name is executed. Shell functions are executed in the current shell context; no new process is created to interpret them.
Functions are declared using this syntax:
     [function] name () compound-command [redirections]

Q: Explain controlling bash Features and Options.

Answer:
Controlling bash features and options is explained using command line options and the set.
Command Line Options
Two kinds of command line options are available: short and long. Short options consist of a hyphen followed by a letter; long options have two hyphens followed by multiple characters. Long options must appear before short options on a command line that calls bash.

Bash features
•   Invoking Bash: Command line options that you can give to Bash.
•   Bash Startup Files: When and how Bash executes scripts.
•   Bash Variables: List of variables that exist in Bash.
•   Shell Arithmetic: Arithmetic on shell variables.
•   Printing a Prompt: Controlling the PS1 string.

Q: How can you process the Command Line?

Answer:
Whether we are working interactively or running a shell script, bash needs to read a command line before it can start processing it—bash always reads at least one line before processing a command. When bash recognizes a command that covers more than one line, it reads the entire command before processing it. In interactive sessions bash prompts we with the secondary prompt as we type each line of a multiline command until it recognizes the end of the command:
After reading a command line, bash applies history expansion and alias substitution to the line.
History expansion is the process that bash uses to turn a history command into an executable command line.
Aliases substitute a string for the first word of a simple command. By default aliases are turned on for interactive shells and off for noninteractive shells.

Q: Define Threads and System Calls.

Answer:

Threads: Threads, like processes, are a mechanism to allow a program to do more than one thing at a time. As with processes, threads appear to run concurrently; the Linux kernel schedules them asynchronously, interrupting each thread from time to time to give others a chance to execute. Conceptually, a thread exists within a process.

System Calls: A system call is implemented in the Linux kernel. When a program makes a system call, the arguments are packaged up and handed to the kernel, which takes over execution of the program until the call completes. A system call isn’t an ordinary function call, and a special procedure is required to transfer control to the kernel.

Q: Explain about Debugging C programs.

Answer:

C programs are particularly challenging to debug because the C language does not limit what we can do. In particular, pointers are not only very powerful and flexible, they can also be dangerous. A large part of debugging C programs involves recognizing, understanding and correcting pointer bugs.

Types of Pointer Bugs
Pointer bugs arise from uninitialized pointers, dangling pointers and incorrect use of arguments to functions.
An uninitialized pointer is simply a pointer variable which is used before it has been given a value.
The second type of pointer bug is the dangling pointer. A dangling pointer refers to an area of memory which is no longer being used for its original purpose.
A third kind of pointer bug is the mistaken parameter bug. This kind of bug can be eliminated by using function prototyping.
Symptoms of Pointer Bugs

   A library function suddenly crashes or produces erroneous results.
Cause: A pointer bug has corrupted the library function.

   The symptoms of a bug change after we insert print statements.
Cause: The print statements changed the code corrupted by the pointer bug.

   Control reaches a particular statement, but not the statement immediately following.
Cause: A pointer bug has corrupted one or both of the statements.

   Our program calls a function, but control never reaches the function.
Cause: A pointer bug has corrupted the call stack or the function.

   Control never returns from a function.
Cause: A pointer bug has corrupted the call stack or the function

Find and Fix Bugs

Fixing bugs is a two-step process. The following are the steps to find and fix bugs as follows:
•   Fill memory with a constant value before you run your program.
•   Eliminate the effects of most dangling pointers by disabling any routine which frees a dynamically allocated data structure.
•   Keep precise records about how you invoked your program.
•   Not to change our program during debugging if we can help it. The smallest changes in our program, or even a change in the order in which functions are linked together may cause the symptoms of pointer bugs to change or disappear.

Q: Why is the Shell So Important?
Answer:

The shell is our interface to executing programs, managing files and directories, etc. Though very few people are aware of it, they use the shell frequently in daily work, e.g., completing file names, using history substitution and aliases. The TCSH shell offers all of these features and a few more, which the average user seldom optimizes.
With a high knowledge of our shell's power, we can decrease the time we need to spend in the shell, and increase the time spent on original tasks.

Q: What do you mean by “File Descriptor”?
Answer:

File Descriptor: An integer that identifies an open file within a process. This number is obtained as a result of opening a file. Operations which read, write, or close a file would take the file descriptor as an input parameter. In many operating system implementations, file descriptors are small integers which index a table of open files. In Unix, file descriptors 0, 1 and 2 correspond to the standard input, standard output and standard error files respectively.

Q: Define TC shell.
Answer:

The TC Shell (tcsh) performs the same function as the Bourne Again Shell and other shells. It provides an interface between us and the Linux operating system. The TC Shell is an interactive command interpreter as well as a high-level programming language.

Q: What are the features common to Bourne Again and TC Shells?
Answer:

Common features are:
   History
   Aliases
   Job control
   Filename substitution
History: The use of history in tcsh is similar to its use in bash. The same event and word designators work in both shells. For example,!328 means to execute event number 328.
Aliases: Defining an alias is another way to minimize our work at the keyboard, and we can also eliminate the need to remember long, awkward commands by creating synonyms that are more meaningful to us.
Job control: Job control is the ability to move processes between the foreground and background. This is very useful when you need to do several things at once, but only have one terminal.
Filename substitution: The TC shell expands the characters *, ? and [] in a pathname just as bash does. The * matches any string of zero or more characters, ? matches any single character, and[] defines a character class, used to match single character appearing within a pair of brackets.

Q: How to working with a command line in a TC Shell? Explain it.
Answer:

Word Completion

The TC Shell completes filenames, commands, and variable name on the command line when we prompt it to do so.
Filename Completion: The TC Shell can complete a file name after we specify a unique prefix.
TILDE Completion: The TC Shell parses a tilde (~) appearing the 1st character of a word and attempts to explain it to a user name when we enter a TAB.
Command and Variable Completion: We can use the same mechanism that we use to list and complete filenames with command and variable names.

Editing the Command Line

The tcsh command line editing feature is similar to that available under bash. We can use either emacs mode commands or vim mode commands. Change to vim mode commands by using bindkey –v and to emacs mode command by using bindkey -e.

Correcting Spelling

Spelling correction can take place only at two times: before and after press RETURN.
Before We Press RETURN: In here two functions are used namely spell-line and spell-word.
After We Press RETURN: The variable named correct controls what tcsh attempts to correct or complete after we press RETURN and before it passes the command line to the command being called. If we do not set correct, tcsh will not correct anything.

Q: What are the advantages and disadvantages of threads?
Answer:

Advantages of threads:
   Thread is very useful to make a program appear to do two things at once.
   While the input or output thread is waiting for a connection, one of the other threads can continue with calculations.
   Using multiple threads inside a process can enable a single process to better utilize the hardware resources available.
   In general, switching between threads requires the operating system to do much less work than switching between processes.
Disadvantages of threads:
   Writing multithreaded programs requires very careful design.
   Debugging a multithreaded program is much, much harder than debugging a single-threaded one
   A program that splits a large calculation into two parts as different threads will not necessarily run more quickly on a single processor machine.

Q: Define Filesystem.
Answer:

A Filesystem is a data structure that usually resides on part of a disk and that holds directories of files. Filesystems store user and system data that are the basis of user’s work on the system and the system’s existence.

Q: Define scanning directories. What are the scanning directory functions?
Answer:

Scanning Directories: Scanning directories are determining the file that resides a particular directory. A common problem on Linux systems is scanning directories.
The scanning directory functions are-
opendir: The opendir function opens a directory and establishes a directory stream.
readdir: The readdir function returns a pointer to a structure detailing the next directory entry in the directory stream dirp.
telldir: The telldir function returns a value that records the current position in a directory stream.
seekdir: The seekdir function sets the directory entry pointer in the directory stream given by dirp.
closedir: The closedir function closes a directory stream and frees up the resources associated with it. It returns 0 on success and -1 if there is an error.

Q: Why should I use an editor?
Answer:

It is very important to be able to use at least one text mode editor. Knowing how to use an editor on our system is the first step to independence. We need it to edit files that influence our environment. As an advanced user, we may want to start writing scripts, or books, develop websites or new programs. Mastering an editor will immensely improve our productivity as well as our capabilities.

Q: What are the disadvantages of LINUX?
Answer:

Disadvantages -
1.Not easy to use (even with the easy-to-use distros)
2.Sometimes lacking hardware support (ie, newer laptop network cards, etc)
3.Lack of newer games
4.Lack of powerful specific software (like CAD, etc)

Q: What are the types of Shell?
Answer:

Different shell types:

sh or Bourne Shell: The Bourne shell is considered the primary shell in scripts. All UNIX systems have it, first of all. Second, the shell is small and fast. It doesn't have the interactive features of the C shell. Many consider the Bourne shell to be the best shell for writing portable UNIX scripts.
bash or Bourne Again shell: Bash is the shell, or command language interpreter, for the GNU operating system. The name is an acronym for the ‘Bourne-Again Shell’.
Bash is largely compatible with sh. It is intended to be a conformant implementation of the ieee posix Shell and Tools portion of the ieee posix specification It offers functional improvements over sh for both interactive and programming use.
Bash is the default shell. Bash is quite portable. It currently runs on nearly every version of UNIX.
csh or The C shell is a command processor that's typically run in a text window, allowing the user to type commands which cause actions. The C shell can also read commands from a file, called a script.

tcsh: TC Shell (tcsh) performs the same function as the Bourne Again Shell and other shells. It provides an interface between us and the Linux operating system. The TC Shell is an interactive command interpreter as well as a high-level programming language.

ksh or the Korn shell: It is backwards-compatible with the Bourne shell and includes many features of the C shell as well, such as a command history, which was inspired by the requests of Bell Labs users. The main advantage of ksh over the traditional Unix shell is in its use as a programming language.

Collected By Dushmanta Nath

AIT Notes for IT 6ht sem

2011-04-16T15:59:00.000-07:00

AIT Notes for IT 6ht sem

Introduction

The Client-Server Model

The most common model for distributing a system is the client-server model. The model is fairly simple to explain and use. The client-server model is a form of distributed computing where one program (the client) communicates with another program (the server)for the purpose of exchanging information.
             Client/server describes the relationship between two computer programs in which one program, the client, makes a service request from another program, the server, which fulfils the request. Although programs within a single computer can use the client/server idea, it is a more important idea in a network. In a network, the client/server model provides a convenient way to interconnect programs that are distributed efficiently across different locations. Computer transactions using the client/server model are very common. For example, to check your bank account from your computer, a client program in your computer forwards your request to a server program at the bank. That program might in turn forward the request to its own client program that sends a request to a database server at another bank computer to retrieve your account balance. The balance is returned back to the bank data client, which in turn serves it back to the client in your personal computer, which displays the information for you.

Q: What Is a Port Number?

Answer:

In computer networking, a port number is part of the addressing information used to identify the senders and receivers of messages. Port numbers are most commonly used with TCP/IP connections. Home network routers and computer software work with ports and sometimes allow you to configure port number settings. These port numbers allow different applications on the same computer to share network resources simultaneously.
Port numbers are associated with network addresses. For example, in TCP/IP networking, both TCP and UDP utilize their own set of ports that work together with IP addresses.
Example:
Port Name = Port 21
Application= FTP port
This is the port used for all FTP based file transfers, such as with programs like FTP Voyager, WS_FTP , Cute FTP , FTP NOW, and many more. (FTP = File Transfer Protocol)

Domain Name System
The Domain Name System (DNS) is a hierarchical naming system built on a distributed database for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most importantly, DNS translates Internet domain and host names to IP addresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites.
            The purpose of the DNS is to provide the TCP/IP community with a mechanism to translate host addresses into IP addresses because all routing is based onan examination of IP addresses. To accomplish this translation process, a series of Domain Name Servers are used to create a distributed database that contains the names and addresses of all reachable hosts on a TCP/IP network. That network can be a corporate intranet, the portion of the Internet operated by an Internet service provider (ISP), or the entire Internet.

Q: What is IP Address?
Answer:

IP Address is a unique numeric identifier, divided into four octets, assigned to machines on the Internet or an intranet. This 32-bit numerical address is used so machines can identify and locate each other for the purpose of sending and receiving data.
There are two kinds of addresses that are widely used on the Internet. One is a person's e-mail address, and the other is the address of a Web site, which is known as a URL.

TCP/IP
Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinct network protocols. IP corresponds to the Network layer (Layer 3) in the OSI model, whereas TCP corresponds to the Transport layer (Layer 4) in OSI. In other words, the term TCP/IP refers to network communications where the TCP transport is used to deliver data across IP networks.
Transmission Control Protocol (TCP) supports the network at the transport layer. Transmission Control Protocol (TCP) provides a reliable connection oriented service. Connection oriented means both the client and server must open the connection before data is sent. TCP is defined by RFC 793 and 1122. TCP provides:
•    End to end reliability.
•    Data packet re sequencing.
•    Flow control.

Layers in the Internet Protocol Stack
A set of network protocol layers that work together. The OSI Reference Model that defines seven protocol layers is often called a stack, as is the set of TCP/IP protocols that define communication over the internet.
Physical Layer:
The Physical Layer is the first and lowest layer in the seven-layer OSI model of computer networking. The Physical Layer is responsible for bit-level transmission between network nodes. The Physical Layer consists of the basic hardware transmission technologies of a network. It is a fundamental layer underlying the logical data structures of the higher level functions in a network.
Data Link Layer:
The Data Link Layer is Layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model.
The Data Link Layer is the protocol layer which transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network segment.
The Network Layer:
The Network Layer is Layer 3 of the seven-layer OSI model of computer networking. The Network Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination host via one or more networks while maintaining the quality of service functions. The Network Layer is responsible for routing packets delivery including routing through intermediate routers.
The Transport Layer:
In computer networking, the Transport Layer provides end-to-end communication services for applications within a layered architecture of network components and protocols. The transport layer provides convenient services such as connection-oriented data stream support, reliability, flow control, and multiplexing. Transport layers are contained in both the TCP/IP model (RFC 1122), which is the foundation of the Internet, and the Open Systems Interconnection (OSI) model of general networking.

The Session Layer:
The Session Layer is Layer 5 of the seven-layer OSI model of networking. The Session Layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e. a semi-permanent dialogue. Session Layer services are commonly used in application environments that make use of remote procedure calls (RPCs).
The Application Layer:
The Internet Protocol Suite (TCP/IP) and the Open Systems Interconnection model (OSI model) of computer networking each specify a group of protocols and methods identified by the name Application Layer.
In TCP/IP, the Application Layer contains all protocols and methods that fall into the realm of process-to-process communications across an Internet Protocol (IP) network. Application Layer methods use the underlying Transport Layer protocols to establish host-to-host connections.

The Link Layer Ethernet and IEEE 802 Encapsulation Trailer Encapsulation

Q: What is Ethernet?
Answer:
Ethernet is a protocol that controls the way data is transmitted over a local area network (LAN). It uses wires (meaning it is not a wireless technology).
The IEEE 802.3 standard defines Ethernet at the physical and data link layers of the OSI network model. Most Ethernet systems use the following:
•    Carrier-sense multiple-access with collision detection (CSMA/CD) for controlling access to the network media.
•    Use baseband broadcasts
•    A method for packing data into data packets called frames
•    Transmit at 10Mbps, 100Mbps, and 1Gbps.

Serial Line Internet Protocol
Serial Line Internet Protocol (SLIP) is a TCP/IP protocol used for communication between two machines that are previously configured for communication with each other. It is commonly used on dedicated serial links and dial-up connections that operate at speeds between 1200bps and 19.2Kbps or higher. SLIP has become popular for connecting home system to the internet through RS-232 serial port found on almost every computer and high speed modem.
SLIP modifies a standard Internet datagram by appending a special SLIP END character to it, which allows datagrams to be distinguished as separate. SLIP requires a port configuration of 8 data bits, no parity, and EIA or hardware flow control. SLIP does not provide error detection, being reliant on other high-layer protocols for this. Over a particularly error-prone dial-up link therefore, SLIP on its own would not be satisfactory.

SLIP framing works:

    Break an IP datagram into bytes.
    Send the END character (value “192”) after the last byte of the datagram; in better implementations, send the END character before the first byte as well.
    If any byte to be sent in the datagram is “192”, replace it with “219 220”.
    If any byte to be sent is “219”, replace it with “219 221”.

Point-to-Point Protocol
The Point-to-Point Protocol (PPP) originally emerged as an encapsulation protocol for transporting IP traffic over point-to-point links. PPP also established a standard for assigning and managing IP addresses, asynchronous and bit-oriented synchronous encapsulation, network protocol multiplexing, link configuration, link quality testing, error detection, and option negotiation for added networking capabilities.

PPP provides a method for transmitting datagrams over serial point-to-point links, which include the following three components:
      • A method for encapsulating datagrams over serial links
      • An extensible LCP to establish, configure, and test the connection
      • A family of NCPs for establishing and configuring different network layer protocols

PPP is capable of operating across any DTE/DCE interface. PPP does not impose any restriction regarding transmission rate other than those imposed by the particular DTE/DCE interface in use. Six fields make up the PPP frame. The PPP LCP provides a method of establishing, configuring, maintaining, and terminating the point-to-point connection.

Compressed SLIP

Compressed SLIP (CSLIP) is a common enhancement of today's SLIP implementation. CSLIP uses Van Jacobson header compression algorithm, which relies on the fact that most of the IP and TCP header remains constant during a connection. The current state of a TCP/IP connection is maintained by each endpoint of a link to enable compression and reconstruction of the TCP/IP
header.Up to 16 TCP connections can be handled on the same link by CSLIP.

IEEE 802 Encapsulation

When we talk about Local Area Network (LAN) technology the IEEE 802 standard may be heard. This standard defines networking connections for the interface card and the physical connections, describing how they are done. The 802 standards were published by the Institute of Electrical and Electronics Engineers (IEEE). The 802.3 standard is called Ethernet.
The Ethernet standard data encapsulation method is defined by RFC 894. RFC 1042 defines the IP to link layer data encapsulation for networks using the IEEE 802 standards. The 802 standards define the two lowest levels of the seven layer network model and primarily deal with the control of access to the network media. The network media is the physical means of carrying the data such as network cable. The control of access to the media is called media access control (MAC).

The 802 standards are listed below:
•    802.1 - Internetworking
•    802.2 - Logical Link Control *
•    802.3 - Ethernet or CSMA/CD, Carrier-Sense Multiple Access with Collision detection LAN *
•    802.4 - Token-Bus LAN *
•    802.5 - Token Ring LAN *
•    802.6 - Metropolitan Area Network (MAN)
•    802.7 - Broadband Technical Advisory Group
•    802.8 - Fiber-Optic Technical Advisory Group
•    802.9 - Integrated Voice/Data Networks
•    802.10 - Network Security
•    802.11 - Wireless Networks
•    802.12 - Demand Priority Access LAN, 100 Base VG-AnyLAN
Logic Link Control (IEEE 802.2)
Logic Link Control (LLC) is the IEEE 802.2 LAN protocol that specifies an implementation of the LLC sub layer of the data link layer. IEEE 802.2 LLC is used in IEEE802.3 (Ethernet) and IEEE802.5 (Token Ring) LANs to perform these functions:
1.    Managing the data-link communication
2.    Link Addressing
3.    Defining Service Access Points (SAPs)
4.    Sequencing
Token Bus: IEEE 802.4 LAN Protocol
Token Bus is a LAN architecture using token passing access over a bus topology. Token bus was standarized by the IEEE 802.4 Working Group. The IEEE 802.4 standard for a token-passing bus LAN (local area network) provides for a single media access protocol for use with multiple physical layers.
Token Ring: IEEE 802.5 LAN Protocol
Token Ring is a LAN protocol defined in the IEEE 802.5 where all stations are connected in a ring and each station can directly hear transmissions only from its immediate neighbor. Permission to transmit is granted by a message (token) that circulates around the ring.

Q: What is CSMA/CD?
Answer:
Carrier Sense Multiple Access with Collision Detection (CSMA/CD) is the protocol used in Ethernet networks and this provides specific rules for allowing stations to communicate over the same transmission medium. There are a number of steps involved in communicating with CSMA/CD.
Stations must listen for a carrier on the wire. If no carrier is detected, stations can begin transmitting. While transmitting, the station continues to listen on the wire to ensure successful communications. If two stations attempt to transmit information at the same time, the transmissions overlap and cause a collision.
If a collision occurs, the transmitting station recognizes the interference on the network and transmits a bit sequence called jam. The jam helps to ensure that the other transmitting station recognizes that a collision has occurred. After a random delay, the stations attempt to retransmit the information and the process begins again.

Introduction to ARP and RARP

Address Resolution Protocol (ARP)
The Address Resolution Protocol (ARP) is a computer networking protocol for determining a network host's Link Layer or hardware address when only its Internet Layer (IP) or Network Layer address is known. This function is critical in local area networking as well as for routing internetworking traffic across gateways (routers) based on IP addresses when the next-hop router must be determined.
ARP has been implemented in many types of networks, such as Internet Protocol (IP), DECNET, Token Ring, FDDI, IEEE 802.11 and other LAN technologies, as well as the modern high capacity networks, such as Asynchronous Transfer Mode (ATM).
The ARP protocol is used to map IP addresses to MAC addresses.
ARP Packet Format:

Reverse Address Resolution Protocol (RARP)
The Reverse Address Resolution Protocol (RARP) is an obsolete computer networking protocol used by a host computer to request its Internet Protocol (IPv4) address from an administrative host, when it has available its Link Layer or hardware address, such as a MAC address.
Reverse address resolution protocol (RARP) is used for diskless computers to determine their IP address using the network. The RARP message format is very similar to the ARP format. When the booting computer sends the broadcast ARP request, it places its own hardware address in both the sending and receiving fields in the encapsulated ARP data packet. The RARP server will fill in the correct sending and receiving IP addresses in its response to the message. This way the booting computer will know its IP address when it gets the message from the RARP server.
The Reverse ARP Protocol is used to map MAC addresses to IP addresses.
RARP Packet Format:

Proxy ARP

A proxy is a device that works on behalf of another device. Thus, a proxy ARP represents a mechanism that enables a device to answer an ARP request on behalf of another device. The rationale for the development of proxy ARP, which is also referred to as ARP Hack, dates to the early use of subnetting when a LAN could be subdivided into two or more segments. If a station on one segment required the MAC address of a station on another subnet, the router would block the ARP request because it is a Layer 2 broadcast, and routers operate at Layer 3.Because the router is aware of both subnets, it could answer an ARP request on one subnet on behalf of other devices on the second subnet by supplying its own MAC address. The originating device will then enter the router’s MAC address in its ARP cache and will correctly transmit packets destined for the end host to the router.

ICMP

Internet Control Message Protocol
Internet Control Message Protocol (ICMP) defined by RFC 792 and RFC 1122 is used for network error reporting and generating messages that require attention. The errors reported by ICMP are generally related to datagram processing. ICMP only reports errors involving fragment 0 of any fragmented datagrams. The IP, UDP or TCP layer will usually take action based on ICMP messages. ICMP generally belongs to the IP layer of TCP/IP but relies on IP for support at the network layer. ICMP messages are encapsulated inside IP datagrams.
ICMP will report the following network information:
•    Timeouts
•    Network congestion
•    Network errors such as an unreachable host or network.
The ping command is also supported by ICMP, and this can be used to debug network problems.
ICMP Messages:
The ICMP message consists of an 8 bit type, an 8 bit code, an 8 bit checksum, and contents which vary depending on code and type.
ICMP Message Classes:
At the highest level, ICMP messages are divided into two classes:
o    Error Messages: These messages are used to provide feedback to a source device about an error that has occurred. They are usually generated specifically in response to some sort of action, usually the transmission of a datagram. Errors are usually related to the structure or content of a datagram, or to problem situations on the internetwork encountered during datagram routing.
o    Informational (or Query) Messages: These are messages that are used to let devices exchange information, implement certain IP-related features, and perform testing. They do not indicate errors and are typically not sent in response to a regular datagram transmission. They are generated either when directed by an application, or on a regular basis to provide information to other devices. An informational ICMP message may also be sent in reply to another informational ICMP message, since they often occur in request/reply or solicitation/advertisement functional pairs.
Dynamic Routing
Dynamic routing protocols are supported by software applications running on the routing device (the router) which dynamically learn network destinations and how to get to them and also advertise those destinations to other routers. This advertisement function allows all the routers to learn about all the destination networks that exist and how to to those networks.
A router using dynamic routing will 'learn' the routes to all networks that are directly connected to the device. Next, the router will learn routes from other routers that run the same routing protocol (RIP, RIP2, EIGRP, OSPF, IS-IS, BGP etc). Each router will then sort through it's list of routes and select one or more 'best' routes for each network destination the router knows or has learned. Dynamic routing protocols will then distribute this 'best route' information to other routers running the same routing protocol, thereby extending the information on what networks exist and can be reached. This gives dynamic routing protocols the ability to adapt to logical network topology changes, equipment failures or network outages 'on the fly'.
The purpose of a dynamic routing protocol is to:
•    Discover remote networks
•    Maintaining up-to-date routing information
•    Choosing the best path to destination networks
•    Ability to find a new best path if the current path is no longer available
Static Routing
Static routing is not really a routing protocol. Static routing is simply the process of manually entering routes into a device's routing table via a configuration file that is loaded when the routing device starts up. As an alternative, these routes can be entered by a network administrator who configures the routes manually. Since these manually configured routes don't change after they are configured (unless a human changes them) they are called 'static' routes.
Static routing is the simplest form of routing, but it is a manual process. Static routing also does not handle failures in external networks well because any route that is configured manually must be updated or reconfigured manually to fix or repair any lost connectivity.
Advantages of static routing:
(a)    It can backup multiple interfaces/networks on a router. (b) Easy to configure, (c) No extra resources are needed, (d) More secure
Disadvantages of static routing:
(a)    Network changes require manual reconfiguration (b) Does not scale well in large topologies

UDP

User Datagram Protocol:

The User Datagram Protocol (UDP) is the second transport layer protocol supported by the TCP/IP protocol suite, using which, programs running on different computers on a network can send short messages known as Datagrams to one another. UDP is a connectionless protocol. This means that an application using UDP can have its data transported in the form of IP datagrams without first having to establish a connection to the destination. This also means that when transmission occurs via UDP, there is no need to release a connection, simplifying the communications process. The following protocols or services use UDP:
•    DNS
•    SNMP
•    BOOTP
•    TFTP
•    NFS
•    RPC
•    RIP
UDP Message Format:
The UDP header includes:
1.    Source port number (16 bits) - An optional field
2.    Destination port number (16 bits)
3.    UDP length (16 bits)
4.    UDP checksum (16 bits)

The UDP Header

This header consists of 64 bytes, followed by actual user data. In comparing the TCP and UDP headers, it is easy to note the relative simplicity of the latter because it lacks many of the features of the former. For example, because it does not require the acknowledgment of datagrams nor sequence datagrams, there is no need for Sequence and Acknowledgment fields. Similarly, because UDP does not provide a flow control mechanism, the TCP Window field is removed. The result of UDP performing a best-effort delivery mechanism is a relatively small transport layer protocol header, with the protocol relatively simple in comparison to TCP. The best way to understand the operation of UDP is via an examination of its header. Note that similar to TCP, an IP header will prefix the UDP header, with the resulting message consisting of the IP header, UDP header, and user data referred to as a UDP datagram.

UDP Checksum

The Checksum field is two bytes in length. The use of this field is optional and its value is set to 0 if the application does not require a checksum. If a checksum is required, it is calculated on what is referred to as a pseudoheader. The pseudo-header is a logically formed header that consists of the Source and Destination addresses and the Protocol field from the IP header. By verifying the contents of the two address fields through its checksum computation, the pseudo-header ensures that the UDP datagram is delivered to the correct destination network and host on the network. This does not verify the contents of the datagram.

Q: What do you mean by cookies?

Answer:
Cookies are message given to a Web browser by a Web server. The browser stores the message in a text file. The message is then sent back to the server each time the browser requests a page from the server.
The main purpose of cookies is to identify users and possibly prepare customized Web pages for them. When you enter a Web site using cookies, you may be asked to fill out a form providing such information as your name and interests. This information is packaged into a cookie and sent to your Web browser which stores it for later use. The next time you go to the same Web site, your browser will send the cookie to the Web server. The server can use this information to present you with custom Web pages.

FTP

File Transfer Protocol (FTP)

FTP actually stands for File Transfer Protocol. It is a standard network protocol used to copy a file from one host to another over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and serve
Client and Server
There are two machines involved in an ftp transaction, a client machine, which is sometimes called the local host, and a server machine, which is sometimes called the remote host. The client is always the machine that initiates the transfer. During an ftp session, it is extremely important to keep track of which machine is the client and which is the server, because this will determine whether you use a get command or a put command to move files. The get command is always used to copy files from the server to the client, and the put command is used to copy files from the client to the server.

The benefits of FTP are:

It allows you to send a file ‘as-is’ from your computer to a student’s UNIX account, an anonymous FTP site where they can access it from home, a computer lab or across the country; it is a relatively safe means of transferring data with little chance for error; and it is quick and easy to use.

Simple Mail Transfer Protocol
Simple Mail Transfer Protocol (SMTP) is used to send mail across the internet. There are four types of programs used in the process of sending and receiving mail. They are:
•    MUA - Mail users agent. This is the program a user will use to type e-mail. It usually incorporates an editor for support. The user types the mail and it is passed to the sending MTA.
•    MTA - Message transfer agent is used to pass mail from the sending machine to the receiving machine. There is a MTA program running on both the sending and receiving machine. Send mail is a MTA.
•    LDA - Local delivery agent on the receiving machine receives the mail from its MTA. This program is usually procmail.
•    Mail notifier - This program notifies the recipient that they have mail. Normally this requires two programs, biff and comsat. Biff allows the administrator or user to turn on comsat service.
The MTA on both machines use the network SMTP (simple mail transfer protocol) to pass mail between them, usually on port 25.
SMTP Commands:
•    HELO - Sent by client with domain name such as mymachine.mycompany.com.
•    MAIL - From <myself@mymachine.mycompany.com>
•    RCPT - To <myfriend@theirmachine.theirorg.org>
•    DATA - Sends the contents of the message. The headers are sent, then a blank line, then the message body is sent. A line with "." and no other characters indicates the end of the message.
•    QUIT

Sub netting

•    A subnet is a physical segment in a TCP/IP environment that uses IP addresses derived from a single network ID.
•    By partitioning the bits in the host ID into two parts, Subnet ID and the Host ID, a single Network Address can be used to uniquely define a set of subnets.
•    The number of hosts available for the Network address will be distributed among the subnets.
Subnet Mask and IP

•    A subnet mask is a 32-bit address used to block or “mask” a portion of the IP address to distinguish the network ID from the host ID.
•    Each host on a TCP/IP network requires a subnet mask, either a default subnet mask or a custom subnet mask.
•    A default subnet mask is used on TCP/IP networks that are not divided into subnets.
•    In the subnet mask, all bits that correspond to the network ID are set to 1. All bits that correspond to the host ID are set to 0.

                                                                                                                              [ Edited By Dushmanta ]

Expert System Notes for IT 6th Sem

2011-04-16T15:58:00.000-07:00

Expert System Notes for IT 6th Sem

Q: What is an Expert System?
Answer:

Expert systems are a recent product of artificial intelligence. An expert system is a system
that uses human knowledge captured in a computer to solve problems that ordinary required
human expertise.
An expert system is an interactive computer based decision tool that uses both facts and heuristics to solve difficult decision making problems, based on knowledge acquired from an expert.
An expert system is a model and associated procedure that exhibits, within a specific domain, a degree of expertise in problem solving that is comparable to that of a human expert.
An expert system compared with traditional computer:
Inference engine + Knowledge = Expert System
( Algorithim + Data structure = Program in traditional computer )

Importance of Expert system:
(a) Without expert systems most customers will have no use for large amounts of processing power.
(b)Without expert systems no-one will be able to program complex parallel architectures.

Q: What is shell?
Answer:

A shell is a special purpose tool designed based on the requirements of particular applications. User should supply the knowledge base to the shell. Example for the shell is EMYCIN (Empty MYCIN) shell. Shell manages the input and output. It processes the information given by the user, relates it to the concepts contained in the knowledge base, and provides solution for a particular problem.

Advantage and Disadvantage of Expert System

Advantages:

1. Expert systems do not forget, but human expert may forget.
2. An expert system needs the symbolic representation.
3. It reduces the risk of doing business.
4. It provides the permanent documentation of the decision process.
5. An Expert system can review all the transactions but human expert system can only review a sample.
6. Expert system able to deal with uncertainty.
7. Expert systems are not focus on abstract. It delivers the answer to goal oriented of the interview

Disadvantages:

1. Expert system has no any common sense.
2.Expert system cannot respond creatively to unusual situation.
3. Expert system must be explicitly updates while any changes in environments.
4. Expert system is currently dependent on symbolic input.
5. Measuring the performance of an expert system is difficult because we do not know how to quantify the use of knowledge.
6. An Expert system has access to highly specific domain knowledge.

The Applications of Expert System

The spectrum of applications of expert systems technology to industrial and commercial problems is so wide as to defy easy characterization. The applications find their way into most areas of knowledge work. They are as varied as helping salespersons sell modular factory-built homes to helping NASA plan the maintenance of a space shuttle in preparation for its next flight.
Applications tend to cluster into seven major classes.

Diagnosis and Troubleshooting of Devices and Systems of All Kinds
This class comprises systems that deduce faults and suggest corrective actions for a malfunctioning device or process. Medical diagnosis was one of the first knowledge areas to which ES technology was applied (for example, see Shortliffe 1976), but diagnosis of engineered systems quickly surpassed medical diagnosis. There are probably more diagnostic applications of ES than any other type. The diagnostic problem can be stated in the abstract as: given the evidence presenting itself, what is the underlying problem/reason/cause?

Planning and Scheduling
Systems that fall into this class analyze a set of one or more potentially complex and interacting goals in order to determine a set of actions to achieve those goals, and/or provide a detailed temporal ordering of those actions, taking into account personnel, materiel, and other constraints. This class has great commercial potential, which has been recognized. Examples involve airline scheduling of flights, personnel, and gates; manufacturing job-shop scheduling; and manufacturing process planning.

Configuration of Manufactured Objects from Subassemblies
Configuration, whereby a solution to a problem is synthesized from a given set of elements related by a set of constraints, is historically one of the most important of expert system applications. Configuration applications were pioneered by computer companies as a means of facilitating the manufacture of semi-custom minicomputers (McDermott 1981). The technique has found its way into use in many different industries, for example, modular home building, manufacturing, and other problems involving complex engineering design and manufacturing.

Financial Decision Making
The financial services industry has been a vigorous user of expert system techniques. Advisory programs have been created to assist bankers in determining whether to make loans to businesses and individuals. Insurance companies have used expert systems to assess the risk presented by the customer and to determine a price for the insurance. A typical application in the financial markets is in foreign exchange trading.

Knowledge Publishing
This is a relatively new, but also potentially explosive area. The primary function of the expert system is to deliver knowledge that is relevant to the user's problem, in the context of the user's problem. The two most widely distributed expert systems in the world are in this category. The first is an advisor which counsels a user on appropriate grammatical usage in a text. The second is a tax advisor that accompanies a tax preparation program and advises the user on tax strategy, tactics, and individual tax policy.

Process Monitoring and Control
Systems falling in this class analyze real-time data from physical devices with the goal of noticing anomalies, predicting trends, and controlling for both optimality and failure correction. Examples of real-time systems that actively monitor processes can be found in the steel making and oil refining industries.

Design and Manufacturing
These systems assist in the design of physical devices and processes, ranging from high-level conceptual design of abstract entities all the way to factory floor configuration of manufacturing processes

MAJOR COMPONENTS OF EXPERT SYSTEMS

TheUserInterface
The user interface is the means of communication between a user and the expert systems problem-solving processes. A good expert system is not very useful unless it has an effective interface. It has to be able to accept the queries or instructions in a form that the user enters and translate them into working instructions for the rest of the system. It also has to be able to translate the answers, produced by the system, into a form that the user can understand. Careful attention should be given to the screen design in order to make the expert system appear ‘friendly’ to the user.

TheKnowledgeBase
The knowledge base stores all the facts and rules about a particular problem domain. It makes these available to the inference engine in a form that it can use. The facts may be in the form of background information built into the system or facts that are input by the user during a consultation. The rules include both the production rules that apply to the domain of the expert system and the heuristics or rules-of-thumb that are provided by the domain expert in order to make the system find solutions more efficiently by taking short cuts.

The Shell or Inference Engine
The inference engine is the program that locates the appropriate knowledge in the knowledge base, and infers new knowledge by applying logical processing and problem-solving strategies.

Q: What are the characteristics of Expert System?
Answer:

    The most obvious feature of an expert system is that it operates as an interactive system that responds to questions, asks for clarifications, makes recommendations and generally aids the decision-making process.
    Expert system tools have the ability to store and sift through significant amounts of knowledge.
    Not only must such a system be able to store the available knowledge, but it must also support mechanisms to expand and improve the knowledge base on a continuing basis.
    An expert system must have the capability to make logical inferences based on the knowledge stored.
    A feature somewhat unique to expert systems is that a particular system caters to a relatively narrow area of specialization. Expert systems are very domain-specific.
    The applications best suited for expert systems are those dealing with expert heuristics for solving problems.
    Expert systems have become increasingly popular because of their specialization, albeit in a narrow field.

Q: Explain the types of Expert System.
Answer:

There are many different types of expert systems. The following list describes the various types.
Diagnosis. Diagnosis types of expert systems are used to recommend remedies to illnesses, trouble-shoot electronic or mechanical problems or as debugging tools.

Repair. Expert systems that define repair strategies are also very common. As well as diagnosing the problem they can suggest a plan for the repair of the item. The repair plan typically contains a scheduling structure and some control structure to validate the repair process. Such systems have been employed in the automotive repair field and similar areas.
Instruction. Instructional expert systems have been used for individualised training or instruction in a particular field. The system presents material in an order determined by its evaluation of the user’s ability and current knowledge and monitor’s the progress of the student, altering the sequence depending on this progress.
Interpretation. Interpretive expert systems have the ability to analyse data to determine its significance or usefulness. The knowledge base often contains models of real world situations which it compares to its data. These are often used in exploration for mineral, gas and oil deposits as well as in surveillance, image analysis and speech understanding.

Prediction. Predictive expert systems are used as a method to “guess” at the possible outcomes of observed situations, usually providing a probability factor. This is used often in weather forecasting.

This allows experts to quickly develop solutions that save time. These systems do not replace experts but act as a tool by performing tasks such as costing, building design, material ordering and magazine design.

Monitoring and Control. In certain applications expert systems can be designed to monitor operations and control certain functions. These are particularly useful where speed of decision making is vitally important, for example in the nuclear energy industry, air traffic control and the stock market.
Classification/Identification. These systems help to classify the goals in the system by the identification of various features (these can by physical or non-physical) For example various types of animals are classified according to attributes such as habitat, feeding information, colour, breeding information, relative size etc.

Q: What is Knowledge Engineering?Explain.
Answer

Knowledge Engineering is an engineering discipline that involves integrating knowledge into computer systems in order to solve complex problems normally requiring a high level of expertise. It refers to the building, maintaining and development of systems. It is used in many computer science domains such as artificial intelligence including databases, data mining, expert systems, decision support systems and geographic information systems.
It mainly involves two types of people:
    Knowledge Engineer
    Human Expert
Knowledge Engineer: A knowledge engineer is a computer systems expert who is trained in the field of expert systems. Receiving information from domain experts, the knowledge engineers interpret the presented information and relay it to computer programmers who code the information in to systems databases to be accessed by end-users.
Human Expert: Human experts are people who specialize in a particular field. A human expert will reach a conclusion, a decision is made or recommended goal is achieved. For example:Docter is a human expert in the medical field.

Q: What is the difference between Deep knowledge and Shallow knowledge?
Answer:

Knowledge is deep when it concerns the central ideas of a topic or discipline, which are judged to be crucial to it. Deep knowledge involves establishing relatively complex connections to those central concepts.
Knowledge is shallow, thin or superficial when it is not connected with significant concepts or central ideas of a topic or discipline, and is dealt with only in an algorithmic or procedural fashion. Knowledge is also shallow when important, central ideas have been trivialized by the teacher or students, or when it is presented as non-problematic.

KNOWLEDGE REPRESENTATION SYSTEMS
Knowledge representation systems, also called expert systems, are computerized models that capture the knowledge of one or more human experts and store it in the framework that is most appropriately suited to the reasoning processes that the experts use in their problem-solving behavior. Such systems are created by a specialized systems analyst called a knowledge engineer, whose task is to interview the expert and/or observe his problem-solving behavior, then determine the most appropriate form(s) of knowledge representation to model the expert's problem-solving techniques. This process, called knowledge acquisition, is perhaps the most difficult and time-consuming aspect of expert systems development. It requires both technical and people skills on the part of the knowledge engineer, who must establish rapport with the domain expert, maintain a productive relationship during the interviewing process, and recognize the required mapping from the expert's explanations to the appropriate knowledge representation. The knowledge engineer then encodes the expert's knowledge into a knowledge base, which is a repository of the expert's knowledge in a particular representational structure.
In addition to the knowledge base, an expert system includes an automated reasoning mechanism called an inference engine that performs calculations and/or logical processes to produce the results of a particular problem-solving session. The explanation facility of an expert system provides the user with an explanation of the reasoning process that was used to achieve the conclusion or recommendation. Each knowledge representation has a corresponding inference technique. Three very common knowledge representations are rule-based systems, frame-based systems, and case-based systems.
Logic Frames:
Logic frames are literal strings representing knowledge of facts, operations or inductive or deductive rules. Logic frames are nested and serve as both a data structure and an inference and constraint mechanism.

Need of frames
Frame is a type of schema used in many AI applications including vision and natural language processing. Frames provide a convenient structure for representing objects that are typical to a stereotypical situation. The situations to represent may be visual scenes, structure of complex physical objects, etc. Frames are also useful for representing commonsense knowledge. As frames allow nodes to have structures they can be regarded as three-dimensional representations of knowledge.
A frame is similar to a record structure and corresponding to the fields and values are slots and slot fillers. Basically it is a group of slots and fillers that defines a stereotypical object. A single frame is not much useful. Frame systems usually have collection of frames connected to each other. Value of an attribute of one frame may be another frame.

Semantic Nets :
A semantic net (or semantic network) is a knowledge representation technique used for propositional information. So it is also called a propositional net. Semantic nets convey meaning. Semantic nets are two dimensional representations of knowledge. Mathematically a semantic net can be defined as a labeled directed graph.
Semantic nets consist of nodes, links (edges) and link labels. In the semantic network diagram, nodes appear as circles or ellipses or rectangles to represent objects such as physical objects, concepts or situations. Links appear as arrows to express the relationships between objects, and link labels specify particular relations. Relationships provide the basic structure for organizing knowledge. The objects and relations involved need not be so concrete. As nodes are associated with other nodes semantic nets are also referred to as assiciative nets.

Disadvantage of Semantic Nets
One of the drawbacks of semantic network is that the links between the objects represent only binary relations. For example, the sentence Run(Chennai Express, Chennai,Bangalore,Today) cannot be asserted directly.
There is no standard definition of link names.
Advantages of Semantic Nets
    Semantic nets have the ability to represent default values for categories. In the above figure Jack has one leg while he is a person and all persons have two legs. So persons have two legs has only default status which can be overridden by a specific value.
    Semantic nets convey some meaning in a transparent manner
    Semantic nets are simple and easy to understand.
    Semantic nets are easy to translate into PROLOG.

Q: What is DENDRAL?
Answer:

DENDRAL was the first Expert system to be completed. It was developed at Stanford University in late 1960s.The system was capable of determining the structure of chemical compounds. Suppose that an organic chemist wants to know the chemical nature of some substance. The first step is to determine the number of atoms of various kinds in one molecule of the stuff. This step determines the chemical formula. Once a sample’s chemical formula is known, the chemist may use the sample’s mass spectrogram to work out the way the atoms are arranged in the chemical’s structure, thus identifying the isomer of the chemical.
DENDRAL has following features:

(1) Knowledge representation: Production rules and algorithm for generating graph structure are constructed by META- DENDRAL. META DENDRAL is a program which uses learning techniques to construct rules for an expert system automatically.
(2) Reasoning: DENDRAL uses forward chaining.
(3) Heuristics: DENDRAL uses generate and test method.
(4) Explanation: the user can supply the information and the system can request information as required.
(5) Working: The spectrogram machine bombard a sample with high energy electrons, causing the molecule to break up into charged chunks of various sizes. Then, the machine sorts the chunks by passing them through a magnetic field which deflects the high-charge, low-weight ones more than it does the low-charge, high charges ones. it is now possible to get an estimate of the masses of these particles. This is called a mass spectrogram. By knowing the masses, it is possible to guess how the atoms of a single molecule of the unknown substance are put together.

Q: What is MYCIN ?
Answer:

Mycin is an Expert system for diagnosing and recommending treatment of bacterial infection of blood. It was developed in Stanford University in California. A consolation with MYCIN begins with request for routine information such as age, medical history, and so on, progressive to more specific questions as required.MYCIN represented its knowledge as a set of if……….THEN rules with certainty factors.

MYCIN has following features:

(1)Domain: Medical diagnosis for bacterial and meningitis infections.
(2)Task: interview physician, make diagnosis and therapy recommendations
(3)Input: Answers to queries.
(4)Output: Ordered set of diagnoses and therapies.
(5)Architecture: rule-based exhaustive backward chaining with uncertainty.
(6)Tools: programmed in LISP (shell called EMYCIN -- empty MYCIN).
(7) Results: not in general use, but was ground-breaking work in diagnostic consultation systems.

Q: What is a Fuzzy Expert System?
Answer:
A fuzzy expert system is an expert system that uses fuzzy logic instead of Boolean logic. In other words, a fuzzy expert system is a collection of membership functions and rules that are used to reason about data. Unlike conventional expert systems, which are mainly symbolic reasoning engines, fuzzy expert systems are oriented toward numerical processing.
The rules in a fuzzy expert system are usually of a form similar to the following:
    if x is low and y is high then z = medium
where x and y are input variables (names for now data values), z is an output variable (a name for a data value to be computed), low is a membership function (fuzzy subset) defined on x, high is a membership function defined on y, and medium is a membership function defined on z. The part of the rule between the "if" and "then" is the rule's premise or antecedent. This is a fuzzy logic expression that describes to what degree the rule is applicable. The part of the rule following the "then" is the rule's conclusion or consequent. This part of the rule assigns a membership function to each of one or more output variables. Most tools for working with fuzzy expert systems allow more than one conclusion per rule.

A typical fuzzy expert system has more than one rule. The entire group of rules is collectively known as a rule base or knowledge base. Fuzzy expert systems are the most common use of fuzzy logic. They are used in several wide-ranging fields, including:
•    Linear and nonlinear control.
•    Pattern recognition.
•    Financial systems.

Q: List major knowledge representation methods.
Answer:

a) Logical Representation
     First Order Predicate Calculus
     Prolog
b) Procedural Representation
     if… then … rules
c) Network Representation
     Semantic networks
     Conceptual graphs
d) Structured Representation
     Scripts
     Frames and objects

Q: What kind of mistakes might ES make and why? Why is it easier to correct mistakes in ES than in conventional programs?
Answer:

As ES mimics a human expert, it is capable of making mistakes as much as the expert does. For example, if the expert provides wrong rules, the system will make a wrong diagnosis. Also, ES frequently work with incomplete infor¬mation. Therefore, they provide probabilistic advice, e.g., they are not sure about a certain interpretation or about a diagnosis. For example, the expert system identifies a certain malfunction with a certainty factor of .8. This means that the system could be incorrect 20% of the time.
In addition to using wrong rules and providing probabilistic answers, the system may ask, like a human expert, wrong questions from the user.
However, since we separate the knowledge base from the inference engine, and the knowl¬edge is organized in a non-sequential manner (i.e., in indepen¬dent rules), it is easy to correct mistakes once detected.

Q: Define natural language processing.
Answer:

Natural language processing is a program that permits (to a certain degree) a human-computer dialogue in a conversational, day-to-day language (a natural language like English, French, or Dutch). It is a field of computer science and linguistics concerned with the interactions between computers and human (natural) languages.

Inferencing:

Inferencing is the reasoning process of AI (artificial intelligence). It takes place in the brain of an AI process.

Q: What is knowledge elicitation?
Answer:

Knowledge elicitation can be described ‘as acquiring knowledge from human experts and learning from data’.
There are three major stages to this procedure:
•    Initial understanding and structuring of the domain (environment, tasks, information flow, concept and attributes).
•    Producing the first working system (extract relationships between domain concepts)
•    Testing and debugging the system.

Q: Define knowledge base, interpreter, scheduler, inference engine, Lisp?
Answer:

A knowledge base is a special kind of database for knowledge management, providing the means for the computerized collection, organization, and retrieval of knowledge.
An interpreter normally means a computer program that executes, i.e. performs, instructions written in a programming language. An interpreter may be a program that either executes the source code directly or translates source code into some efficient intermediate representation (code)
Scheduling is a key concept in computer multitasking, multiprocessing operating system and real-time operating system designs.
The inference engine is the generic control mechanism that applies the axiomatic knowledge present in the knowledge base to the task-specific data to arrive at some conclusion. This is the second key component of all expert systems.

Lisp (or LISP) is a family of computer programming languages with a long history and a distinctive, fully parenthesized syntax. Lisp is the second-oldest high-level programming language in widespread use today.

Conceptualization
The collection of objects, concepts and other entities that are assumed to exist in some area of interest and the relationships those hold among them. A conceptualization is an abstract, simplified view of the world that we wish to represent. For example, we may conceptualize a family as the set of names, sexes and the relationships of the family members. Choosing a conceptualization is the first stage of knowledge representation.

[Collected By Dushmanta ]

MIS Notes for IT 6th sem

2011-04-16T15:53:00.000-07:00

MIS Notes for IT 6th sem

INTRODUCTION

Definition: Management Information Systems (MIS) is the term given to the discipline focused on the integration of computer systems with the aims and objectives on an organization.
The development and management of information technology tools assists executives and the general workforce in performing any tasks related to the processing of information. MIS and business systems are especially useful in the collation of business data and the production of reports to be used as tools for decision making.

Application Of MIS:
 MIS systems can be used to transform data into information useful for decision making. Computers can provide financial statements and performance reports to assist in the planning, monitoring and implementation of strategy.

 MIS systems provide a valuable function in that they can collate into coherent reports unmanageable volumes of data that would otherwise be broadly useless to decision makers. By studying these reports decision-makers can identify patterns and trends that would have remained unseen if the raw data were consulted manually.

 MIS systems can also use these raw data to run simulations – hypothetical scenarios that answer a range of ‘what if’ questions regarding alterations in strategy. For instance, MIS systems can provide predictions about the effect on sales that an alteration in price would have on a product. These Decision Support Systems (DSS) enable more informed decision making within an enterprise than would be possible without MIS systems.

Programmed Decision Marking:
Programmed decisions are best in highly structured environments with established goals and channels of information. Because of the high structure, it’s possible to set up a rule that states an action will take place once a certain condition has been reached. This streamlines general, repetitive, and frequent decisions.
Programmed decisions enable upper management to dictate the decisions of middle management by establishing the rules. It also enables a small business owner to make quick and consistent decisions by setting a rule and applying it to all similar decisions.
After establishing the rules across a series of decisions, the rules guide future decisions to make decision making more efficient and effective.
Programmed decisions are proactive. They anticipate future problems and establish decision making to resolve the problems
Non-Programmed Decision Marking:
Non-programmed decision making occurs in opposite conditions than programmed decision making. The environment most appropriate for non-programed decision making is one with poor structure, vague goals or ambiguous information. Usually decision making in such environments requires information and analysis specific to each decision.
Non-programmed decision making applies to specific concerns and infrequent decisions so that no rule can guide decisions.
Non-programmed decision making is reactive rather than proactive. Because the problems are more difficult to anticipate, each problem has to be dealt with as it occurs.

Significance of MIS:

MIS have become a vital component of successful business firms and other organizations. They contribute an essential field of study in business administration and management. That’s why business managers must take a subject in information systems. Since you intend to be a manager or business professional it is very important to have a basic understanding of information systems as it is to understand any other functional area in business. The following are the reasons why Information systems are important.

1. Information system Resources and technologies:
An information system is an organized combination of people, hardware, software communication network and data resources that collects, transfer the information in organization. End users work by using many types of information system. They might include simple manual hardware devices and informal communication channels.

2. An end user perspective:
Anyone who uses information system or information it produces is an end user. This usually related to all persons in an organization are distinguished from the smaller number of persons who are information system analysts or professional computer programmers. A manager end user is a manager or professional who personally uses information systems so most managers are managerial end users.

3. An enterprise perspective:
Information system plays a vital role in business success of an enterprise. Information technology can provide the information. A business needs for efficient operations, effective management and competitive advantage. However if information system don’t properly related to the strategic objectives, business operations or management needs of an enterprise they can seriously damage its success so the proper management of information system is a major challenge for managers.

4. A global society perspective:
We are living in a global info society, with a global economy that is increasingly dependent on the creation, management and distribution of information dependent on creation. So information is the basic resource in today’s society.

MIS model:

In the MIS model, the database contains the data provided by the subsystem. In addition both data and information are entered from environment. The database contents are used by software that product periodic and special reports as well as mathematical models that perform various aspects of the firms operation. The software output are used by people who are responsible for solving the firm’s problems. Note that some of problem solvers can exist within the firm’s environment. The MIS provides information to other members of inter organizational information system.

Components of MIS:

 Process: The total process of a system is the net contribution of many individual processes in MIS design. This is accomplished by ongoing activities in converting inputs to outputs. For example if we consider typical marketing information system, the fundamental inputs and outputs could be processed as follows:
Inputs:
1. Sales on units by each salesman for a period.
2. Estimated sales in units of competitor corresponding to above.
3. Economic conditions and trends.
Outputs:
1. Sales by product i.e. month wise and till date.
2. Sales by salesman i.e. month wise and till date.
3. Sales by trend analysis.
4. Sales forecasting.
For conversion of output from inputs it is important to classify transfer, aggregate and analyze input quantities to get desired outputs variables. This enables the current information at any specific point of time.

 Parameters of MIS:
An introduction of new technologies, restructuring of sales staff or discovery of new market spaces result in constant variations in sales, forecasting reports. These quantities which describe state of system are called the parameters of MIS.

 Boundaries of MIS:
Any system is identified by certain limiting factors which includes its components processes and inter relationships. These limiting factors are termed as boundaries of a system. Effective interface can be built among various systems by identification of various boundaries. Example: a teller of accounts in the bank is a system which contributes to the activities of deposits withdraws and related activities affecting the customer bank balance.

Characteristics of MIS:

The Basic characteristics of an effective Management Information System are as follows:

I. Management-oriented: The basic objective of MIS is to provide information support to the management in the organization for decision making. So an effective MIS should start its journey from appraisal of management needs, mission and goal of the business organization. It may be individual or collective goals of an organization. The MIS is such that it serves all the levels of management in an organization i.e. top, middle and lower level.

II. Management directed: When MIS is management-oriented, it should be directed by the management because it is the management who tells their needs and requirements more effectively than anybody else. Manager should guide the MIS professionals not only at the stage of planning but also on development, review and implementation stages so that effective system should be the end product of the whole exercise in making an effective MIS.

III. Integrated: It means a comprehensive or complete view of all the sub systems in the organization of a company. Development of information must be integrated so that all the operational and functional information sub systems should be worked together as a single entity. This integration is necessary because it leads to retrieval of more meaningful and useful
information.

I V. Common data flows: The integration of different sub systems will lead to a common data flow which will further help in avoiding duplicacy and redundancy in data collection, storage and processing. For example, the customer orders are the basis for many activities in an organization viz. billing, sales for cashing, etc. Data is collected by a system analyst from its original source only one time. Then he utilizes the data with minimum number of processing procedures and uses the information for production output documents and reports in small numbers and eliminates the undesirable data. This will lead to elimination of duplication that simplify the operations and produce an efficient information system.

V. Heavy planning-element: The preparation of MIS is not a one or two day exercise. It usually takes 3 to 5 years and sometimes a much longer period. So the system expert has to keep 2 things in mind – one is that he has to keep future objectives as well as the firm’s information well in advance and also he has to keep in mind that his MIS will not be obsolete before it gets into action.

VI. Sub System concept: When a problem is seen in 2 sub parts, then the better solution to the problem is possible. Although MIS is viewed as a single entity but for its effective use, it should be broken down in small parts or subsystems so that more attention and insight is paid to each sub system. Priorities will be set and phase of implementation will be made easy. While making or breaking down the whole MIS into subsystems, it should be kept in mind that the subsystems should be easily manageable.

VII. Common database: This is the basic feature of MIS to achieve the objective of using MIS in business organizations. It avoids duplication of files and storage which leads to reduction in costs. Common database means a “Super file or Master file” which consolidates and integrates data records formerly stored in many separate data files. The organization of the database allows it to be accessed by each subsystem and thus,eliminates the necessity of duplication in data storage, updating, deletion and protection.

VIII. Computerized: MIS can be used without a computer. But the use of computers increases the effectiveness and the efficiency of the system. The queries can be handled more quickly and efficiently with the computerized MIS. The other benefits are accuracy,storage capacity and timely information.

IX. User friendly/Flexibility: An MIS should be flexible i.e. there should be room for further modification because the MIS takes much time in preparation and our environment is dynamic in nature.MIS should be such that it should be used independently by the end user so that they do not depend on the experts.

X. Information as a resource: Information is the major ingredient of any MIS. So, an MIS should be treated as a resource and managed properly

Evolution of MIS:

In starting all business were local and small in operation. A single individual perform all activities by himself. Single individual was responsible for production of goods, for storage and for the exchanging purpose to the outside environment. There was practically no need for record keeping because the person knew that how much of stock he had made etc. But over years business started growing and along with growth business complexities also increased i.e. from one or two commodities to several thousand products, with localized operations to global operations with production facilities and wide marketing in many counties. The chief executive of such a big corporation has to depend on reports, mostly periodic paper reports for information. It is impossible for him to visit all his corporation facilities, warehouses etc. It is the operation system that keeps him informed of his corporation activities such full-fledged information. System requires an organized system to collect data at source with accuracy, process it and keep all his files updated to feed the manager with most current highly accurate information needing investment. Data is used in the form of raw material and must be subjected to data processing to produce useful information and information system produces this useful information by using data. If the information system generates information which is useful for managers in planning and control then the whole system is called MIS.
The evolution of MIS and its growth depends on following:
1. On growth of management theory and techniques
2. On growth of management accounting and its applications in business.
3. On changes in the production and distribution methods.

MIS support for decision making:

Decisions vary with respect to structure that can be provided for making them. Basically the decisions are of two types:

1.Structured: A highly structured decision can be preplanned or pre specified. Structure decision is also said to be programmable decision in the sense that unambiguous decisions rules can be specified in advance. It doesn’t mean that the decision is automated although making programmable decisions are automated. The structured program decision tends to be routine and frequently repeated.

2.Unstructured: They are not preplanned or pre-specified the unstructured decisions tend to occur with less frequency and tends to be non-routine. The unstructured decision has no pre-established decision procedure.

Conceptual Structure of MIS:
The conceptual structure of an information system consists of a group of information subsystems for different functions. Each subsystem provides support for transaction processing,operational control, management control and strategic planning. The conceptual structure includes some unique files for each subsystem plus a common database. There is unique software for each subsystem and there is common software used by all subsystems, i.e. a data management system, some software routines, planning & decision models.
Physical Structure of MIS:
The actual organizational information system will defer from the above model because certain elements are not cost justified. The physical structure of an information system is affected by the use of common modules for many processing operations. It is designed as an informational system with a number of small sets of processing instructions called modules. These modules can be written and tested separately allowing more efficient maintenance by identification of the
boundaries of the module being changed.

INFORMATION CONCEPT

Q: Write the definition of DSS.
Answer: A decision support system (DSS) is a computer-based information system that supports business or organizational decision-making activities. DSSs serve the management, operations, and planning levels of an organization and help to make decisions, which may be rapidly changing and not easily specified in advance.
DSSs include knowledge-based systems. A properly designed DSS is an interactive software-based system intended to help decision makers compile useful information from a combination of raw data, documents, personal knowledge, or business models to identify and solve problems and make decisions.
Characteristics of a DSS.
1. Facilitation. DSS facilitate and support specific decision-making activities and/or decision processes.
2. Interaction. DSS are computer-based systems designed for interactive use by decision makers or staff users who control the sequence of interaction and the operations performed.
3. Ancillary. DSS can support decision makers at any level in an organization. They are NOT intended to replace decision makers.
4. Repeated Use. DSS are intended for repeated use. A specific DSS may be used routinely or used as needed for ad hoc decision support tasks.
5. Task-oriented. DSS provide specific capabilities that support one or more tasks related to decision-making, including: intelligence and data analysis; identification and design of alternatives; choice among alternatives; and decision implementation.
6. Identifiable. DSS may be independent systems that collect or replicate data from other information systems OR subsystems of a larger, more integrated information system.
7. Decision Impact. DSS are intended to improve the accuracy, timeliness, quality and overall effectiveness of a specific decision or a set of related decisions.
Application of DSS
DSS is extensively used in business and management. Executive dashboard and other business performance software allow faster decision making, identification of negative trends, and better allocation of business resources.
A growing area of DSS application, concepts, principles, and techniques is in agricultural production, marketing for sustainable development.

DSS are also prevalent in forest management where the long planning time frame demands specific requirements. All aspects of Forest management, from log transportation, harvest scheduling to sustainability and ecosystem protection have been addressed by modern DSSs. A comprehensive list and discussion of all available systems in forest management is being compiled under the COST action Forsys
Types Of Decision Support System:
There are a number of Decision Support Systems. These can be categorized into five types:
• Communication-drivenDSS
Most communications-driven DSSs are targetted at internal teams, including partners. Its purpose are to help conduct a meeting, or for users to collaborate. The most common technology used to deploy the DSS is a web or client server. Examples: chats and instant messaging softwares, online collaboration and net-meeting systems.
• Data-drivenDSS
Most data-driven DSSs are targeted at managers, staff and also product/service suppliers. It is used to query a database or data warehouse to seek specific answers for specific purposes. It is deployed via a main frame system, client/server link, or via the web. Examples: computer-based databases that have a query system to check (including the incorporation of data to add value to existing databases.
• Document-drivenDSS
Document-driven DSSs are more common, targeted at a broad base of user groups. The purpose of such a DSS is to search web pages and find documents on a specific set of keywords or search terms. The usual technologies used to set up such DSSs are via the web or a client/server system. Examples:
• Knowledge-drivenDSS:
Knowledge-driven DSSs or 'knowledgebase' are they are known, are a catch-all category covering a broad range of systems covering users within the organization seting it up, but may also include others interacting with the organization - for example, consumers of a business. It is essentially used to provide management advice or to choose products/services. The typical deployment technology used to set up such systems could be silent/server systems, the web, or software running on stand-alone PCs.
• Model-drivenDSS
Model-driven DSSs are complex systems that help analyse decisions or choose between different options. These are used by managers and staff members of a business, or people who interact with the organization, for a number of purposes depending on how the model is set up - scheduling, decision analyses etc. These DSSs can be deployed via software/hardware in stand-alone PCs, client/server systems, or the web.

DSS Users:

Managers, knowledge workers and staff specialists in a wide variety of professions, occupations, industries and disciplines. DSS users include internal and external stakeholders of an organization. Ultimately, anyone who makes decisions and has access to a computer is a potential user of a DSS.

Q: What is a Group Decision Support System?

Answer:

A Group Decision Support System (GDSS) is an interactive, computer-based system that facilitates solution of unstructured problems by a set of decision-makers working together as a group. It aids groups, especially groups of managers, in analyzing problem situations and in performing group decision making tasks. A GDSS is a hybrid system that uses an elaborate communications infrastructure and heuristic and quantitative models to support decision-making.

Q: What are the characteristics of GDSS?

Answer:
 Special Design to accommodate requirements of group decision-making environment.
 Must support ease of use
 Flexibility to be utilized by different decision making styles and levels.
 Anonymous Input
 Reduction of negative group behavior.
 Support of positive group behavior
 May require specialized software depending upon decision-making settings.

Q: What is Executive Support System?

Answer:

Executive Support System (ESS) is a reporting tool that allows you to turn your organization's data into useful summarized reports. These reports are generally used by executive level managers for quick access to reports coming from all company levels and departments such as billing, cost accounting, staffing, scheduling, and more.

Characteristics Of ESS

Tailored to individual executives
Easy to use
Drill down capabilities
Support the need for external data
Help with situations with high degree of uncertainty
Futures orientation (predictions, forecasting)
Linked with value-added business processes.
Executive Information Systems

Definition: An Executive Information System (EIS) is a set of management tools supporting the information and decision-making needs of management by combining information available within the organization with external information in an analytical framework.

Advantages of EIS
• Easy for upper-level executives to use, extensive computer experience is not required in operations
• Provides timely delivery of company summary information
• Information that is provided is better understood
• Filters data for management
• Improves to tracking information
• Offers efficiency to decision makers
Disadvantages of EIS
• System dependent
• Limited functionality, by design
• Information overload for some managers
• Benefits hard to quantify
• High implementation costs
• System may become slow, large, and hard to manage
• Need good internal processes for data management
• May lead to less reliable and less secure data

Definition of Organization

An organization is a social arrangement which pursues collective goals, controls its own performance, and has a boundary separating it from its environment.
A social unit of people, systematically structured and managed to meet a need or to pursue collective goals on a continuing basis. All organizations have a management structure that determines relationships between functions and positions, and subdivides and delegates roles, responsibilities, and authority to carry out defined tasks. Organizations are open systems in that they affect and are affected by the environment beyond their boundaries.

Classification of Information System

The two most common classifications are:
1. Classification by breath of support
2. Classification by organizational level

Classification by Breath of Support:

Typical information systems that follow the hierarchical organization structure are functional (departmental), enterprise wide and interorganizational.
Functional information systems are organized around the traditional departments.
Enterprise information systems serve several departments or the entire enterprise.
Interorganizational systems connect two or more organizations.

Classification by Organization Level:

The typical enterprise is organized hierarchically, with the clerical and office worker layer, the operational layer, the managerial layer, the knowledge worker layer and finally the strategic layer.

Data:
Data is raw facts and figures unprocessed (meaningless). Data relates to fact, event and transactions.
Information:
Information is data that has been processed in such a way as to be meaningful to the person who receives it. It is anything that is communicated.

Introduction to ERP

Q: What is ERP?
Answer:

ERP is one of the most widely implemented business software systems in a wide variety of industries and organizations. ERP is the acronym of Enterprise Resource Planning. ERP is just not only software. ERP definition refers to both; ERP software and business strategies that implement ERP system.
ERP implementation utilizes various ERP software applications to improve the performance of organizations for
1) resource planning,
2) management control and
3) operational control.

Components of an ERP System:

1) ERP software,
2) Business Processes that ERP software supports,
3) Users of ERP systems, and
4) Hardware and Operating Systems that run ERP applications.

ERP Evaluation:

ERP evaluation refers to the systematic procedures followed to estimate the performance of ERP in a company. This is not a one step process and it should be a part of the organizational study and as well as be done from time to time.
The first thing in ERP evaluation is ROI. ERP is a very costly investment and it becomes very important to check if the returns are satisfactory or justified for the costs involved. ERP evaluation is dependent on several factors. As a matter of fact implementation of ERP will eat up a large chunk of the organizations profits in many cases. The reason is that ERP calls for change management and before the employees tune in to the new atmosphere the company might have to lose several regular businesses. This will certainly prove to be useful if only ERP satisfies the requirements of the company and is able to compensate on this loss.
Similarly lot of money is spent on implementing ERP and training the workforce to use it. Apart from all this it has to be studies if ERP has facilitated smooth transaction of business than ever. This is one of the most important parameter in assessment which decides if ERP should be a part of the organization or if it should be given a go by.

Advantages (Benefits of ERP):

Integration
Integration can be the highest benefit of them all. The only real project aim for implementing ERP is reducing data redundancy and redundant data entry. Those companies where integration is not so important or even dangerous, tend to have a hard time with ERP. ERP does not improve the individual efficiency of users, so if they expect it, it will be a big disappointment. ERP improves the cooperation of users.

Efficiency
Generally, ERP software focuses on integration and tend to not care about the daily needs of people. I think individual efficiency can suffer by implementing ERP. the big question with ERP is whether the benefit of integration and cooperation can make up for the loss in personal efficiency or not.

Costreduction
It reduces cost only if the company took accounting and reporting seriously even before implementation and had put a lot of manual effort in it. If they didn't care about it, if they just did some simple accounting to fill mandatory statements and if internal reporting did not exists of has not been fincancially-oriented, then no cost is reduced.

Less personnel
Less reporting or accounting personnel, but more sales assistants etc.

Accuracy
No. People are accurate, not software. What ERP does is makes the lives of inaccurate people or organization a complete hell and maybe forces them to be accurate (which means hiring more people or distributing work better), or it falls.

Disadvantages of ERP:

Expensive:
This entails software, hardware, implementation, consultants, training, etc. Or you can hire a programmer or two as an employee and only buy business consulting from an outside source, do all customization and end-user training inside. That can be cost-effective.

Not very flexible:
It depends. SAP can be configured to almost anything. In Navision one can develop almost anything in days. Other software may not be flexible.

Application of ERP:
• ERP applications include real time analysis and reporting tools that give you unprecedented insight and control over your operations and are accessible from Pocket Pcs, PDAs and smart phones and capable of deployment across multiple locations.
• Our comprehensive ERP application helps you achieve the goal of continuous improvement in your manufacturing operations.
• ERP applications can be purchased as a collection or one at a time and tightly integrated with your existing systems.

Supply chain management (SCM):

SCM is the management of a network of interconnected businesses involved in the ultimate provision of product and service packages required by end customers. Supply chain management spans all movement and storage of raw materials, work-in-process inventory, and finished goods from point of origin to point of consumption (supply chain)

TPS (Transaction Processing Systems):

TPS is an acronym describing Transaction Processing Systems. TPS systems are exactly what the name implies - a system that processes transactions that occur within an organization or business. TPS systems tend to perform routine operations and serve as a foundation for other systems. Transactions are business operations such as customer orders, purchase orders, receipts, time cards, invoices, payroll checks and, yes, college registrations

Integrated system.

A system in which separate programs perform separate functions with communication and data-passing between functional programs performing standardized I/O routines and a common data-base is called integrated system

Q: What is Quality Control?

Answer:
Quality control is a process employed to ensure a certain level of quality in a product or service. It may include whatever actions a business deems necessary to provide for the control and verification of certain characteristics of a product or service. The basic goal of quality control is to ensure that the products, services, or processes provided meet specific requirements and are dependable, satisfactory, and fiscally sound. Essentially, quality control involves the examination of a product, service, or process for certain minimum levels of quality
Open and Close system:
A closed system is defined as a system which is self-contained. It does not exchange material, information or energy with its environment for example system in manufacturing are often designed to minimize unwanted exchanges with the environment outside the system, so that manufacturing process can operate without disturbance from supplier, customer etc. A computer program is also relatively closed systems because it accepts only previously defined inputs, process them & provides previously defined outputs.
Open system exchanges information, material & energy with the environment i/c random & undefined inputs, examples are biological system & organizational system.
[ Edited By Dushmanta]