While studying about operating system,its useful to study about the services of an operating system.
An operating system provides services to programs and to the users of those programs.The operating system service provides an environment for the execution of programs.The services provided by one operating system is totally different from the other operating system.The operating system makes the programming task much easier.
The most common services provided by the operating system are:
1.Program Execution
2.I/O Operation
3.File System Manipulation
4.Communications
5.Error Detection
1.Program Execution:
Normally the operating system loads a program into the memory and it executes the program.The program must be able to end its execution,either normally or abnormally.
2.I/O Operation:
I/O Operation is one of the service of an operating system.I/O means any file or any specific I/O device.The program may require any I/O device while running time.So the operating system must provide the required I/O.
3.File System Manipulation:
Normally the Program needs to read a file or write a file.the operating system gives the permission to the program for operation on file.
4.Communication:
Communication may be implemented by 2 methods.
a)Shared Memory
b)Message Passing
The Data transfer between two processes is required for some time.Bothe the processes are on the one computer or on the different computer,but it must be connected through a computer network.
5.Error Detection:
Error may occur in CPU,in I/O devices or in the memory hardware.The operating system constantly needs to be aware of the possible errors.It should take the appropiate action to ensure the correct and consistent computing.
The Operating System with multiple users provides the following services:
1.Resource Allocation
2.Accounting
3.Protection
1.Resource Allocation:
If there are more than one user or jobs running at the same time,then the resources must be allocated to each of them.This is called Resource Allocation.Operating system manages different types of resources.Some resources requires the special allocation code.That is the main memory,CPU cycles and the file storage.For allocating CPU,CPU scheduling algorithms are used for the better utilization of CPU.
2.Accounting:
Logs of each user must be kept.It is also necessary to keep record of which user uses how much and what kinds of computer resources.This log is used for accounting purposes.
3.Protection:
Protection involves ensuring that all the access to the system resources is controlled.Security starts with each user having to authenticate to the system,usually by means of a password.In protection all the access to the resources is controlled.
These are the Operating System Services.