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Operating Systems
What is an operating system? Most computer users have had some experience with an operating system, but it is difficult to pin down precisely what an operating system is. Part of the problem is that operating systems perform two basically unrelated functions, and depending on who is doing the talking, you hear mostly about one function or the other. The Operating System as an Extended Machine Just as the operating system shields the programmer from the disk hardware and presents a simple file-oriented interface, it also conceals a lot of unpleasant business concerning interrupts, timers, memory management, and other low-level features. In each case, the abstraction presented to the user of the operating system is simpler and easier to use than the underlying hardware. In this view, the function of the operating system is to present the user with the equivalent of an extended machine or virtual machine that is easier to program than the underlying hardware. The Operating System as a Resource Manager We can view an operating system as a resource allocator. A computer system has many resources (hardware and software) that may be required to solve a problem: CPU time, memory space, file storage space, I/O devices, and so on. The operating system acts as the manager of these resources and allocates them to specific programs and users as necessary for their tasks. Since there may be many, possibly conflicting, requests for resources, the operating system must decide which requests are allocated resources to operate the computer system efficiently and fairly. [Sources: (Tanenbaum, 1987) Andrew S. Tanenbaum, Operating Systems – Design and Implementation (Silberschatz, Galvin, 1994) Abraham Silberschatz, Peter B. Galvin, Operating System Concepts]
 

 

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