The three basic concepts used for the realization of

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Unformatted text preview: e CPUs that have the ability to simultaneously execute several programs. In such a system, instructions from different and independent programs can be processed simultaneously by different CPUs or the CPUs may simultaneously execute different instructions from the same program. 20. Time-sharing is a mechanism to provide simultaneous interactive use of a computer system by many users in such a way that each user is given the impression that he/she has his/her own computer. It uses multiprogramming with a special CPU scheduling algorithm to achieve this. 21. The memory management module of an operating system manages the main memory of the system. Its job is to keep track of which parts of memory are in use and which parts are not in use, to allocate memory to processes when they need it and deallocate when they are done. 22. The uniprogramming memory model is used in uniprogramming systems in which only one job is processed by the system at a time and all the system resources are exclusively available for the job till it completes. 23. In a multiprogramming memory model, multiple user processes can simultaneously reside in the main memory. The two memory management schemes used to facilitate this are multiprogramming with fixed number of memory partitions and multiprogramming with variable number of memory partitions. In the former scheme, the user area of the memory is divided into a number of fixed-sized partitions. On the other hand, in the latter scheme, the number, size, and location of the partitions vary dynamically as processes come and go. 24. External fragmentation of memory is a situation when enough total free memory space exists to satisfy the memory need of a process, but still the process cannot be loaded because the available free memory is not contiguous (is fragmented into multiple free blocks of memory). 25. Internal fragmentation is a situation when a process is allocated more memory than its actual memory requirement and the additional memory allocated to the process remains unutilized beca...
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This document was uploaded on 04/07/2014.

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