Thursday, December 13, 2007

Assignment #3

Page 56
EXERCISES:1,2,3
A.Explain he following:
Multiprogramming. Why i s it used?
A multiprogramming is a technique used to utilize maximum CPU time by running multiple programs simultaneously. The execution begins with the first program and continuous till an instruction waiting for a peripheral is reached, the context of this program is stored, and the second program is memory is given chance to run. The process continued until all program finished running. Multiprogramming has no guarantee that a program will run is timely manner.
B.Internal Fagmentation. How does it occur?
The internal fragmentation occurs it when a fixedpartition is partially used by program, the remaining space within the partition is unavailable to any other job and that's the time internal fragmentation occur when there is another job followed on the space. So that it will not wasted.
C.Compaction: Why is it need?
Compaction is very needed because it is the process of collecting fragments of available memory space into contiguous in block by moving programs and data in acomputer's memory disks, or known as garbage collection.
E.Relocation: How often should it performed? It depend on the process of address refferences in program.
#2. Describe the Major Disadvantages for each of the four memory allocation schemes presented in the chapter. The disadvantage of this memory allocation its an overhead process, so that while compaction is being done everything else must wait.
#3.Describe the Major Advantages for each of the memory alloatiuon schemes presented in the chapter. They could be divided into segments of variable sizes of equal size. Each page, or segment, could be stored wherever there was an empty block best enough to hold it.

http://www.google.com.ph/search?hl=en&q=multiprogramming.Why+is+it+used&meta=



Page 104
EXERCISE:#4
A:What is the cause of thrashing?
Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault.
B:How does the operating system detect thrashing?
The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming.
C:Once thrashing is detcted, what can the operating system do to iliminate it?
It can be eliminated by reducing the level of multiprogramming .

http://www.go4expert.com/forums/showthread.php?t=834

EXERCISE:#5

What purpose does the referenced bit serve in a demand paging system?
=is it want it to be loaded faster???... it seems that demand paging introduce the concept of loading partial of program into the memory and when begins the pages'll be loaded into the memory as they'r e needed

http://www.daniweb.com/forums/thread8504.html