DISTRIBUTED SYSTEM:
The processors communicate with one another through various communicate lines, such as high speed buses or telephone lines.
These systems are usally reffered to as loosely coupled systems or distributed systems.
The processors in a distributed system vary in size and function. They include small microprocessors, work station, mini computers and larger general purpose computer system. These Processors are reffered to by a no. of different names such as site, modes, computers and so on.
There is variety of reasons for building distributed system, the major one are:
1. Resource Sharing:
If a no. of different sites are connected to one another then a user at one site may be able to use the resource available at another.
Example:
A user at site A may be using printer available at site B. Meanwhile, a user at site B may access a file that resides at A.
2. Computation speed up:
If a particular computation can be partitioned in to a no. of sub computations that can run concurrently then a distributed system may allow as to distribute the computation among the various sites to run that compution concurrently. In addition, if a particular site is currently overloaded with jobs, some of them may moved to other lightly loaded sites. This movement of job is called load sharing.
3. Reliability:
If one site facts in a distributed system, the remaining sites can potentialy continue operating.
4. Communication:
There are many instances in which programs needs to exchange data with one another on one system.
Example:
When many sites are connected by a communication network, the processes at different site the chance to exchange data. They may communicate via electronic mail. User can send to the user at the same site or at a different site.