Overview of UNIX

Posted by Amrita Gautam at May 2, 2021


An operating system is the software that manages all the resources of computer and provides a convenient and safe environment for running programs . Though , there are various operating systems available in the market today like DOS , Windows , UNIX , Linux etc.Amongst these UNIX operating system had arrived in the computer world much earlier then its other operating system.

This chapter will introduce readers to the concept of operating system , types of operating systems , evolution of UNIX operating system , features , architecture and types of files in UNIX.


The operating system is the main part of any computer system . It is responsible for the management and coordination of activities and the sharing of the limited resources of the computer.

The operating system acts as a host for applications that are run on the machine as host,one of the purposes of an operating system is to handle the details of the operating of the hardware.This relieves application programs from having to manage these details of the and makes it easier to write application. Almost all computer , including handheld computer , desktop computer , desktop computer , supercomputer , and even video game consoles , use an operating system of some type . Some of the oldest models may however use an embedded operating system , that may be contained on a computer disk or other data storage device.

Users can also interact with the operating system with some king of software user interface like typing commands by using command line interface or using a graphical user interface.

In Brief we can say the operating system is program which performs following function.

A program that manages the computer hardware.

Provides a basis for application programs and acts as an intermediary between a user of computer and the computer hardware.

The one program running at all times on the computer (usually called the kemel) , with all else being application programs.


Accosding to users we can categorize operating system into two categorios:

1. Singel user

2. Multi-user

1.2.1 Single user

A single-user operating system provides access to the computer system by a single user at a time.

If another user needs access to the computer system , they must wait till the current user finished what they are doing and leaves.

Example: consider a typical home computer. There is a single keyboard and mouse that accept input commands , and a single monitor to display information output.

1.2.2 Multe-user

In a multi-user operating system more then one user can access the computer system at one time. Access to the computer system is normally provided via a network , so that users access the computer remotely using a terminal or other computer.

In the early days of large multi-user computer, multiple terminals (keyboards and associated monitors) were provides. These terminals sent their commands to the main multi-user computer for processing , and the results were displayed on the associated terminal monitor screen. Terminals were hard-wired directly to the multi-user computer system.

Today , these terminals are generally personal computers and use a network to send and receive information to the multi-user computer system. Examples of multi-user operating systems are UNIX, Linux.


It is the first operating system which has given us features if networking and code-usability. Apart from having almost all the common features of other operating system , it also has some additional and unique features which are not in other operating system. It can run on all kinds of hardware and provide open sources code system.

User can interact with the UNIX system through a command line Interpreter called a shall.UNIX basically follows Layered architecture which consists with four major layers hardware , kernel , shall and Utilities.


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