In any computer system it is desirable to maximize

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Unformatted text preview: ce requirements of the job. The command interpretation module of an operating system takes care of interpreting user commands, supplied individually or in the form of command language, and directing the system resources to handle the requests. With this mode of interaction with the system, the user is usually not too concerned with the hardware details of the system, or with how the operating system will direct the hardware to handle certain requests. In addition to the above listed major functions, an operating system also performs few other functions such as keeping an account of which users (or processes) use how much and what kinds of computer resources, maintenance of log of system usage by all users, and maintenance of internal time clock. MEASURING SYSTEM PERFORMANCE The efficiency of an operating system and the overall performance of a computer system is usually measured in terms of the following: 1. Throughput. Throughput is the amount of work that the system is able to do per unit time. It is measured as the number of processes that are completed by the system per unit time. For example, if n processes are completed in an interval of t seconds, the throughput is taken as n/t processes per second during that interval. Throughput is normally measured in processes/hour. Note that the value of throughput does not depend only on the capability of a system, but also on the nature of jobs being processed by the system. For long processes, throughput may be one process/hour; and for short processes, throughput may be 100 processes/hour. 2. Turnaround time. From the point of view of an individual user, an important criterion is how long it takes the system to complete a job submitted by him/her. Turnaround time is the interval from the time of submission of a job to the system for processing to the time of completion of the job. Although higher throughput is desirable from the point of view of overall system performance, individual users are more interested in better turnaround time for their jobs. 3. Response time. Turnaround ti...
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