Dale - Computer Science Illuminated 351

Dale - Computer Science Illuminated 351 - time sharing . A...

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Timesharing A system in which CPU time is shared among multiple interactive users at the same time Virtual machine The illusion created by a timesharing system that each user has a dedi- cated machine 324 Chapter 10 Operating Systems Figure 10.2 In early systems, human operators would organize jobs into batches User User User User Operator Computer Batch Batch job jobs Though most of our computer use these days is interactive, some jobs even today lend themselves to batch processing. For example, processing a corporation’s monthly salary payments is a large job that uses specific resources with essentially no human interaction. Early batch processing allowed multiple users to share a single computer. Though the emphasis has changed over time, batch systems taught us valuable lessons about resource management. The human oper- ator of early computer systems played many of the roles that modern oper- ating system software does now. Timesharing As we pointed out in Chapter 1, the problem of how to make use of the machine’s greater capabilities and speed lead to the concept of
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Unformatted text preview: time sharing . A timesharing system allows multiple users to interact with a computer at the same time. Multiprogramming allowed multiple processes to be active at once, which gave rise to the ability for programmers to interact with the computer system directly, while still sharing its resources. Timesharing systems create the illusion that each user has the computer exclusively. That is, each user does not have to actively compete for resources, though that is exactly what is happening behind the scenes. One user may actually know he is sharing the machine with other users, but does not have to do anything special to allow it. The operating system manages the sharing of the resources, including the CPU, behind the scenes. The word virtual means in effect, though not in essence. In a time-sharing system, each user has his or her own virtual machine , in which all...
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This note was uploaded on 01/13/2011 for the course CSE 1550 taught by Professor Marianakant during the Fall '10 term at York University.

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