Operating systems: design and implementation
Operating systems: design and implementation
Scheduling Processes with Release Times, Deadlines, Precedence and Exclusion Relations
IEEE Transactions on Software Engineering
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Multitasking refers to an operating system's ability to support multiple processes simultaneously. A process is a program in execution. Support for multiple processes is necessary in applications where several computations must proceed in parallel. On a PC, a user may edit a file while another file is being printed and electronic mail (q.v.) is received. These three activities are best supported by three processes running simultaneously. Multitasking is also needed on servers and time-sharing systems where multiple users share a single computer system and all processes created by them should, at least in principle, execute simultaneously. Real-time systems that control multiple devices also need to support multiple processes. For instance, an avionics computer on board an aircraft runs processes for monitoring the engines, updating the flight instruments, processing radar signals, and keeping the airplane on course. Batch operating systems depend on multitasking for overlapping computation with I/O operations: when a process performs I/O, the operating system runs another process to avoid idling the central processor for long periods of time.