(a) Name FOUR techniques for memory management. (b) What is overlaying in progra
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Question
(a) Name FOUR techniques for memory management. (b) What is overlaying in program execution? Give an example for the overlaying operation. (c) A page table of a process is shown in Table 1. Translate the logical addresses in (i) and (ii) into their corresponding physical address and determine if the addresses are valid address or not. Given that the process has the following parameters in its address calculation: starting address = 2400, bound address = 3600 and page size = 400 bytes. (i) Logical address (ii) Logical address (d) Explain thrashing in a virtual memory scheme. (e) A computer system has a main memory module of 4 Gbytes in size and a process of 10 Gbytes in size is going to be executed in the system. Suggest a method to successfully execute the process.Explanation / Answer
a.
Four memory management techniques are:
1. Paging: a process in which main memory is divided into small fixed-sized blocks of (physical) memory called frames and the size of a frame is kept the same. Size of a page is chossen to have optimum utilization of the main memory and to avoid external fragmentation.
2. Segmentation: Segmentation technique in which each process is divided into many segments of different sizes, for every module that contains pieces that perform related functions. Each segment is actually a different logical address space of the program e.g. Code, Stack, heap etc
3. Virtual Memory: A computer can address more memory than the amount physically installed on the system. This extra memory is virtual and the processor thinks that it present in main memory, and can load programs larger than Main Memory size.
4.Demand paging: It is concept that include both virtual mapping and paging. The pages that the processor requests are only loaded into the main memory, and other pages remains in the secondary storage
b.
Overlay is a process of transferring a block of program code or other data into internal memory, replacing what is already stored". This is a method that allows programs to be larger than the the size of main memory present
c.
i>
page: 0
0 maps to 2400 ( 2400 is address in main memory)
200 is added as offset
therefore the logical adderss is 2400, 200 where 2400 is the frame number in main memory and 200 is the offset
ii>
page: 2
2 maps to 3200 %( 3200 is address in main memory)
200 is added as offset
therefore the logical adderss is 3200, 500 where 3200 is the frame number in main memory and 500 is the offset
But if you notice 3200 + 500 is above of range of since 3700 > 3600 so it throws an error .
d.
In computing, virtual memory is a memory management technique that is implemented, It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory. Main storage as seen by a process or task appears as a contiguous address space or collection of contiguous segments. The operating system manages virtual address spaces and the assignment of real memory to virtual memory.
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