home

What is Operating System ?

An operating system is a system software which manages all the resources of a computer, In computing an **operating system** (**OS**) is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of a computer.One of the purposes of an operating system is to handle the resource allocation and protection of the hardware. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling devices such as disk drive and printers.

Every PC has to have one operating system to run other applications or programs. It’s the first thing“loaded”.  What are the functions of OS ?

Today most operating systems perform the following important functions:

 1. Processor management, that is, assignment of processor to different tasks being performed by the computer system.

2. Memory management, that is, allocation of main memory and other storage areas to the system programmes as well as user programmes and data.

3. Input/output management, that is, co-ordination and assignment of the different output and input device while one or more programmes are being executed.

4. File management, that is, the storage of file of various storage devices to another.It also allows all files to be easily changed and modified through the use of text editors or some other files manipulation routines.  5. Interpretation of commands and instructions.

6. Coordination and assignment of compilers, assemblers, utility programs, and other software to the various user of the computer system.

7. Facilities easy communication between the computer system and the computer operator (human). It also establishes data security and integrity.

 Operating systems can be classified as follows:

multi-user  **:** Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.


 * multiprocessing** **:** Supports running a program on more than one CPU.


 * multitasking** **:** Allows more than one program to run concurrently.


 * multithreading** **:** Allows different parts of a single program to run concurrently.


 * real time****:** Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time