Subject: Operating System

Topic: DISTRIBUTED SYSTEMS

Difficulty: Medium

Distributed Operating System is a model where distributed applications are running on multiple computers linked by communications. A distributed operating system is an extension of the network operating system that supports higher levels of communication and integration of the machines on the network.

This system looks to its users like an ordinary centralized operating system but runs on multiple, independent Central Processing Units (CPUs).

These systems are referred as loosely coupled systems where each processor has its own local memory and processors communicate with one another through various communication lines, such as high speed buses or telephone lines. By loosely coupled systems, we mean that such computers possess no hardware connections at the CPU - memory bus level, but are connected by external interfaces that run under the control of software.

The Distributed Os involves a collection of autonomous computer systems, capable of communicating and cooperating with each other through a LAN / WAN. A Distributed Os provides a virtual machine abstraction to its users and wide sharing of resources like as computational capacity, I/O and files etc.

The structure shown in fig contains a set of individual computer systems and workstations connected via communication systems, but by this structure we cannot say it is a distributed system because it is the software, not the hardware, that determines whether a system is distributed or not.

Distributed systems provide the following advantages:

a. Sharing of resources.

b. Reliability.

c. Communication.

d. Computation speedup.