Operating Systems - History of Operating Systems & Basic Operating System Concepts [Class Notes]

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A Brief History of Operating System [Class Notes]

History of Operating Systems
&
Basic Operating System Concepts

 

Suresh Khanal
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http://www.psexam.com

What is an Operating System?

An operating system should be conceived as a combination of following different aspects:-

1. A Program
but with a funny function invocation mechanism. An operating system is no different than any other program, other than it lays on the bottommost layer.

2. A Control Program

controls the execution of programs and devices. An operating sytem is responsible to monitor and control the operation of each and every software as well as hardware components of a computer system.

3. An Interface

An abstract virtual machine. Operating system behaves as a computer system for all other applications so that the communication is possible and the underlying hardware details are encapsulated to provide common standard interface.

4. A Programming Environment

The kernel + utilities

5. A resource manager

The operating system maximizes system performance since it manages the available resources.

6. A service provider

An operating system provides different services to other applications such as File storage, network communications, and so on.

Why do we need operating system?

Today it would appear a funny question. We can't imagine operating a computer without an operating system. But, major reason can be drawn as following two:-

1. They Provide a high-level abstraction of physical resources

Since operating systems provice common standard interface, it enables the construction of more complex software systems. Similarly, without operating system, it would be impossible to imagine portable code.

2. They allow sharing of limited or expensive physical resources

Because operating systems manages the computer resources it is possible to share the expensive physical resources and optimize their use.

A Brief History of Operating Systems

Hand Programmed Machines ('45-'55)

Batch Processing or Offline processing ('55-'65)

Spooling Processing or online processing ('62-'69)

Multiprogramming ('65-'80)

Timesharing('70-  )

Types of Operating Systems

Personal Computing System

Distributed Operating System

Parallel Operating System

Each processor has a copy of the operating system. Many jobs can be executed in parallel.

Master processor allocates jobs to slave processors
 

Real-time Operating System