Computers have operations {computer operations}. Programs can run immediately {interactive processing} {on-line processing} {real-time processing}. Programs can execute later, typically at night when CPU usage is low {batch processing, computer} {off-line processing}. On-line transactions take time {response time} {flowtime} {float time} to process [Luce, 1986].
Computer systems can have two or more processors {multiprocessing}. Job-control program decide job types to do and their priority and puts jobs in job queue.
Operating systems can add and remove program parts {swapping}| {memory swapping} from storage devices into memory {virtual memory}, to use only needed program sections. Virtual memory uses either fixed-length pages or logical program segments.
Operations process many characters per second {throughput}|.
Several users can use CPU at once {timesharing}|, because CPU is fast compared to input rates.
3-Computer Science-Software-Operating System
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Date Modified: 2022.0225