Q. Show the services which provided by operating system?

A) Resource Allocation:

• If there are more than one user or jobs running at the same instance then resources should be allocated to every one of them. Operating system manages various types of resources require special allocation code i.e.CPU cycles, main memory and file storage.

• There are a number of resources that require only general request and release code. For allocating CPU, CPU scheduling algorithms are used for better utilization of CPU. CPU scheduling routines consider the speed of CPU and number of available registers as well as other required factors.

B) Accounting :

• Logs of every user should be kept. It is also essential to keep record of which user how much and what types of computer resources. This log is used for accounting purposes.

• The accounting data can be used for statistics or for the billing. It is also used to improve system efficiency.

C) Protection:

• Protection involves ensuring that all access to system resources is controlled. Security starts with each user having to authenticate to system typically by means of a password. External I/O devices should be also protected from invalid access attempts.

• In protection all the access to the resources is controlled. In multiprocess environment it's possible that one process to interface with the other or with operating system so protection is required.