What is an Operating System

Operating system is a set of programs, which are used to manage overall operations of a computer system in order to achieve maximum efficiency.

A program that acts as an intermediary between a user of a computer and the computer hardware

In other words,

A program that is executed by the processor that frequently relinquishes control and must depend on the processor to regain control.

* A program that mediates between application programs and the hardware.

* A set of procedures that enable a group of people to use a computer system.

* A program that controls the execution of application programs.

* An interface between applications and hardware.

OS is a large collection of software , which manages resources of the computer system, such as memory, process, file system and Input/Output devices

Thus , An Operating system is a set of programs that controls the execution of application programs and acts as an interface between the user of a computer and the computer hardware

An operating system must be capable to perform many functionality . some of these are

* Resource manager

* Protection

* Accounting

* Fault detection and Monitoring

* User friendly resource

* supervision

* interrupt Handling

* Storage management(Primary and Secondary)

* Communication

AS a Resource manager or Resource Allocator the Operating System must perform the following for each resources

* Keep track of the resource.

* Reclaim or deallocate the resources

* Enforce policy that determines who gets what , when and how much

* Allocate the resource to the job decided.

Responsibility of Operating System as a Resource Manager OR SYSTEM CALL

An operating system performs large number of functions. Each function is carried out by a component of the operating system. The components of an operating system are:

1. Process management sub-system

2. Memory management sub-system

3. File management sub-system

4. I/O system management sub-system

5. Secondary storage management sub-system

6. Network management sub-system

7. Protection sub-system

8. User-interface sub-system

An operating system provides an environment for the execution of programs. The operating system provides certain services to programs and to the users of those programs. The specific services provided will differ from one operating system to another, but there are some common classes that we can identify. These operating system services are provided for the convenience of the programmer, to make the programming task easier. Some of these services are listed below:

1. Program execution services

2. I/O operation services

3. File system services

4. Communication services

5. Error detection services

6. Accounting services

7. Protection services

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