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Introduction To UNIX Operating System

  • What is UNIX?
UNIX is an operating system which was first developed in the 1960s. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops. UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available. First version of UNIX developed at the University of California Berkeley.

  • The UNIX Operating System

The UNIX operating system is made up of three parts: 

1. The kernel

2. The shell

3. Utilities 


THE KERNEL

• The kernel of UNIX is the hub of the operating system.

• It allocates time and memory to programs and handles the filestore and communications in response to system calls. 


THE SHELL

Shell is the command line interpreter. 

  • Shell is just another program 

A program or command which interacts with the kernel and it may be any of:

  • built-in shell command

  • interpreted script 

  • compiled object code file 

It searches the filestore for the file containing the program and then requests the kernel through system calls to execute the program.

When the process has finished running the shell then returns the UNIX prompt to the user indicating that it is waiting for further commands.

The shell acts as an interface between the user and the kernel.

When a user logs in, the login program checks the username and password, and then starts another program called the shell.

The shell is a command line interpreter (CLI).

It interprets the commands the user types in and arranges for them to be carried out. The commands are themselves programs.

When they terminate, the shell gives the user another prompt on our systems. 


UTILITIES

• UNIX provides several hundred utility programs, often referred to as commands.

• The commands accomplish universal functions such as printing, editing files, etc. . 


UNIX Operating System

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