An in term of set of applications. User

An operating system is a special type of software designed for the purpose of controlling and managing the execution of applications in the computer and acts as an interface between application programs and computer hardware. Generally, the end user sees the computer system in term of set of applications. User is unaware of computer hardware details. A distributed operating system looks at its users as a general centralized operating system but runs on many independent connected systems. Distributed system uses multiple central processors to serve multiple Real-Time applications and multiple users. Data processing jobs are distributed among the processors accordingly. Processors communicate with each other through various lines (such as high-speed buses or telephone lines). Distributed systems do not share main memory or disks. A distributed operating system is basically a collection of processors connected to a communication network in which each processor has its own local memory and peripheral devices and passing through the communication network between the system’s processor communications happens. The distributed operating system provides a mechanism in which the master operating system splits the work into different slaves and the processor collects the results of all slaves and shows the final result. Distributed operating systems are an extension of the network operating system, where distributed applications are running on many computers connected by communication. Distributed operating systems are designed in a manner that does not have complete information about the system environment. Resources in distributed systems differ physically, there is no normal clock between multiple processors, delivery of messages is delayed and messages can be lost too. Despite all these complexities and difficulties, the distributed operating system should be designed in a way that the user could be able to see a distributed system as a virtual centralized system that is flexible, reliable, secure and easy to use. In order to fulfill this challenge, the designer of distributed operating systems should deal with many design issues. Some of them are as follows: