need and functions of an operating system

NEED AND FUNCTIONS OF AN OPERATING SYSTEM

When a program written in a high level language is executed by a computer, the following steps are followed:

i.                   The compiler compiles the program that is loaded in the memory.

ii.                 The source program is read and loaded in the memory .

iii.    The source program is compiled into the object code. While compiling. If any syntax error is detected in the program appropriate message is printed.

iv.              During compilation, a machine language routines for reading and writing required by the program are brought in from a library of routines stored in a peripheral store and linked to the object program.

v.                 The compiler may now be taken out of the memory as its job is over and the space made available for the data of the program. The object program is now executed. If any error is detected during execution , the contents of various registers in CPU at that time are communicated to the user to aid him in correcting the program.

When a  computer has many languages, many compilers would be available. Therefore, the appropriate compiler should be selected and loaded. The input-output routines for different devices should include monitoring their status and detecting errors. As all programs need them , they are kept in the disk storage with appropriate identification for easy retrieval.

A computer must provide, besides the hardware and high level language translators, many other routines which enable a user to effectively use the system . An operating system provides these routines.

FUNCTIONS OF AN OPERATING SYSTEM

The main functions performed by an operating system are as follows:

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

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

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

4-    File management , that is, the storage of files on various storage devices and the transfer of 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 routines.

5-    Co-ordination and assignment of compilers, assemblers, utility programs and other software to the various users of the computer system.

6-    Establishment of data security and integrity. That is, it keeps different programs and data in such a manner that they do not interfere with each other. It also protects itself from  being destroyed by any user.

7-    Facilities easy communication between the computer system and the computer (human) operator.

8-    Maintenance of internal time clock and log of system usage for all the users.