Introduction to Operating Systems, Basic Operating System Concepts

What is an Operating System?

An Operating system is basically a intermediary agent between the user and the computer

hardware. Manages the computer’s resources (hardware, abstract resources, software)

It’s a resource allocator.It is also used to control programs to prevent errors and improper computer use. It is interrupt driven.

Operating System Benefits

Simplifies hardware control for applications

Enforcer of sharing, fairness and security with the goal of better overall performance

Trade-off between fairness and performance

Trade-off between optimal algorithms and lean algorithms – OS is overhead.

Provides abstract resources Sockets Inter-process communication

History of Operating Systems

Earliest computers had no Operating System

Applications loaded manually

Users were experts on the hardware

First System Software was libraries of code to manage devices.

This grew to batch processing systems, where some focused on application programming and some on systems programming.

Batch Processing

A typical computer in the 1960s and 70s was a large machine.

Its processing was managed by a human operator.

The operator would organize various jobs from multiple users into batches.

  

Timesharing

A timesharing system allows multiple users to interact with a computer at the same time

Multiprogramming allowed multiple processes to be active at once, which gave rise to the ability for programmers to interact with the computer system directly, while still sharing its resources In a timesharing system, each user has his or her own virtual machine, in which all system resources are (in effect)

The IBM 650 Magnetic

Drum Data Processing

System Machine

 

Cray I supercomputer,

introduced in 1976

Current Operating Systems Research Topics

- Symmetric multiprocessing

Allows for several CPUs to process multiple jobs at the same time. CPUs are independent of one another, but each has access to the operating system.

- Asymmetric multiprocessing

Some operating systems functions are assigned to subordinate processors, which take their instructions from the main CPU.

- Distributed processing

Processors are placed at remote locations and are connected to each other via telecom devices. Different from symmetric multiprocessing systems as they do not share memory. Computations can be dispersed among several processors.

Reference :

•Stallings, William, Operating Systems, Second Edition, Prentice-Hall International Editions,

Englewood Cliffs, New Jersey, 1995.

•Tanenbaum, Andrew S., Modern Operating Systems, Prentice-Hall International Editions,

Englewood Cliffs, New Jersey, 1992.

 

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