OPERATING SYSTEMS

An Operating System (OS) is software program that controls the internal activities of the computer hardware and provides user interface. Application programs also need to interact with the operating system for using hardware resources.

            OS is the first program loaded (copied) into the computer’s main memory after the computer is switched on.

An operating system performs the following functions:

(1) Processor Management: The operating system assigns processors (if a computer has more than one processor) to the different tasks that must be performed by the computer system.

(2) Memory Management: Operating system allocates the main memory and secondary memory to the systems programs, user programs and data.

(3) Input/Output Management: It carrier out the input/output management and co-ordinates and assigns different input and output devices.

(4) File Management: It manages files on various storage devices and transfers these files from one storage device to another. It also allows all files to be easily changed and modified through the use of text editors or some other file manipulation software packages.

(5) Security Management: It establishes data security and integrity. That is, it keeps different programs and data in such a manner that they do not interfere each other. Moreover, it also protects data from being destroyed by any other user.

(6) Interpretation of command: For using various system resources, a user communicates with the operating system via a set of commands provided by it. Command interpretation module interprets user commands and directs system resources to process the commands.

All operating systems can be classified into four categories:

(1)Single User Operating System: Operating system which allows only one user to work on a computer at a time is known as single user operating system. Examples include DOS, Windows, etc.

(2)Multiuser Operating System: A multiuser operating system allows a number of users to work together on a single computer. Each user will be provided a terminal connected to a computer. Examples include Linux, UNIX, Windows 2000, etc.

(3) Single Tasking Operating System: Operating system which can execute only a single task at a time is known as single tasking operating system. Example- DOS.

(4) Multitasking Operating System: Multitasking operating system supports execution of more than one job at a time. Most of today’s operating systems such as Windows 2000, OS/2, UNIX, LINUX, etc. support multitasking.