Please help me with this homework The following are multiple choice questions, w

Question

Please help me with this homework The following are multiple choice questions, which can have more than one answer. For each question, give all t lie possible answers. Paging is a memory management method whereby main memory is divided into equal-sized frames, and process images are split into equal-sized pages. Which if the following are true of paging? The size of a page is the size of a frame, that is, each page fits exactly into a frame of memory. A page table is used to map each page of a process into a frame of memory. The page page may use a bit to mark the pages which have read-only code and/or instruct ions. External fragmentation is possible when paging is used. When paging is used, Secondary storage is also organized into blocks of frames which are the same size as a page. Secondary storage is where the process image is stored as the result of a successful compilation. A CPU can execute any process while it is stored in secondary storage. Secondary storage can be used to temporarily store a process which has been swapped out of main memory. Using paging as the memory management method, when a new process is admitted into the ready queue of the system, only a small set of pages, called the working set, may be loaded into main memory, such as the pages containing the main function and its variables. Which of the following are a consequence of this approach? More processes can be admitted into the ready queue keeping the CPU(s) busy. The wait queues for I/O devices are likely to be busy since now any process which needs to reference a page not in memory will need to perform a system call to bring the needed page into memory. The page tables can have a bit to indicate whether a page in the page table of a process is in memory or not. The page table can use a second bit to indicate that a page can be "read only" and any attempt to write to a read only page can be trapped as an error. When paging is used as the memory management system, what can be said about the maximum size of a process? Nothing, the maximum size can be as large as possible. The size of the largest process is the size of main memory. The size of the largest process is the size of secondary storage since only a working set of pages need to be brought into main storage to start execution. The maximum size is less than the size of main memory since the kernel must always be resident in main memory.

Explanation / Answer

1. (a) - A process is divided into a number of pages, and main memory is divided into a number of frames. And page size is equal to the frame size. This technique of memory management is called paging. So, it's true.
(b) - Yes, a page table is required to map the page numbers to a frame number. As the page now can be stored non-contiguously in different frames, this mapping is required. Therefore, it's true.
(c) - True. A valid/invalid bit can be added to the page table to reflect read-only code/instructions
(d) - External fragmentation is not possible in paged memory system. Paging avoids the need of external fragmentation and compaction, as page size is equal to the frame size. So, the page would fit exactly into the frame size wherever a free frame is available. Whereas, some internal fragmentation is there: the processes which are not integer multiples of 'page-size' would have a last page which has some free space. Hence, false.

2) a) False, only main memory is divided into frames.
b) False, both main memory and secondary storage can be used
c) False, CPU can only access the main memory.
d) True, in paging , even parts of processes(pages) can be stored out on secondary storage.

3) a) True, as only a working set is loaded into main memory, there is more space available for more number of pages.
b) True, demand paging requires this.
c) True, valid bit is there to indicate this
d) True, access control information is indicated in this bit

4) a) True, it depends on a process how big it will be.
b) False, in demand paging, part of process in form of pages can be swapped in and out
c) False, secondary memory can contain many processes (including the largest process)
d) False, same reason as (b)

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