Operating Systems – Time Sharing Systems


(A3) Time Sharing Systems

The main idea of time sharing systems is to allow a large number of users to interact with a single computer(system) concurrently.

Hence, it extended the idea of multiprogramming to allow multiple terminals with each-in-use terminal to be associated with one or more jobs.

Hence, the there are spaces for more than one user, each associated with a program or more.

The main objective of these systems is to minimize the response time to user commands.

(and lead to interactive work)



  1. A time sharing system allows many users to share the computer resources simultaneously. In other words, time sharing refers to the allocation of computer resources in time slots to several programs simultaneously. For example a mainframe computer that has many users logged on to it. Each user uses the resources of the mainframe -i.e. memory, CPU etc. The users feel that they are exclusive user of the CPU, even though this is not possible with one CPU i.e. shared among different users.

    The time sharing systems were developed to provide an interactive use of the computer system. A time shared system uses CPU scheduling and multiprogramming to provide each user with a small portion of a time-shared computer. It allows many users to share the computer resources simultaneously. As the system switches rapidly from one user to the other, a short time slot is given to each user for their executions.

    The time sharing system provides the direct access to a large number of users where CPU time is divided among all the users on scheduled basis. The OS allocates a set of time to each user. When this time is expired, it passes control to the next user on the system. The time allowed is extremely small and the users are given the impression that they each have their own CPU and they are the sole owner of the CPU. This short period of time during that a user gets attention of the CPU; is known as a time slice or a quantum.

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