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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
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
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.
- Spring '14