A device , which is used to accept raw data from us , processes them as per our instructions and produces results in the form of information , is known as Computer . Also , we say computer system is a general purpose machine that processes data according to a set of instructions that are stored internally. The instructions can be stored temporarily or permanently in the Computer System .
Functions of Operating System
1. Memory (Storage) Management
(a) It keeps tracks of primary memory i.e. what part of it are in use by whom, what part are not in use etc.
(b) In multiprogramming it decides which process will get memory when and how much.
(c) Allocates the memory when the process or program request it to do so.
(d) Declaims (deallocate) the memory when the process no longer needs it or has been terminated. Out of 10 functions of operating system this is first.
2. Processor Management
(a) Keep tracks of processor and status of process. Program that does this is called traffic controller.
(b) In multiprogramming it decides which process gets the processor when &how much time. This function is called Process Scheduling.
(c) Allocate the processor (CPU) to a process.
(d) Deallocate processor when processor is no longer required.
3. Device Management
(a) Keeps tracks of all devices (peripherals).
(b) Decides which process gets the device when & for how much time.
(c) Allocate the device in the efficient way.
(d) Deallocate devices.
4. File Management
(a) It keeps track of information, its location, uses, status etc. The collective facilities are often known as file system.
(b) Decides who gets the resources.
(c) Allocates the resources.
(d) Deallocates the resources.
By means of passwords & similar other techniques, preventing unauthorized access to programs & data.
6. Control over system performance
Recording delays between request for a service & response from the system.
7. Job accounting
Keeping track of time & resources used by various jobs and/or users.
8. Interaction with the operators
The interaction takes place via the console of the computer in the form of instructions from the operator acknowledging the same, action thereon, as well as informing the operation by means of a display screen of works & problem encountered. Out of 10 functions of operating system this is 8th.
9. Error-detecting aids
Production of dumps, traces, error messages and other debugging and error- detecting aids.
10. Coordination between other softwares and users
Coordination and assignment of compilers, interpretiers, assemblers and other software to the various users of the computer systems.
Types of Operating Systems
1. Single User Systems: In this kind of system the processor or a computer does only one job at a time. That is at one point of time only one task can be performed. For Example : MS-DOS
2. Multi User System: This type of system is used by more than one user. It allows the interaction of one user with the other. It also helps in executing more than one task at a particular time. For Example : Unix and Windows NT. Click here for difference between system software and application software.