Memory Management Questions and Answers

Answer: C

Correct answer: Modulator demodulator

Modem is a contraction of modulator-demodulator, which names the two operations it performs: putting digital data onto an analogue carrier and taking it off again.

Answer: A

Correct answer: compaction

Compaction shuffles the allocated blocks to one end so that the free space forms one large hole instead of many small ones. It requires that relocation be done at run time, which is why the next question matters.

Answer: B

Correct answer: page number

The page number indexes the page table; the entry found there gives the frame number, which replaces it to form the physical address.

Answer: D

Correct answer: no matter which algorithm is used, it will always occur

Every contiguous allocation scheme leaves gaps as processes of different sizes come and go, so the placement strategy affects how much external fragmentation occurs but cannot prevent it. Only non-contiguous allocation removes the problem.

Answer: B

Correct answer: cache

A cache sits between two levels working at different speeds - processor and memory, or memory and disk - and holds recently used items so the faster side need not wait for the slower one.

Answer: A

Correct answer: FIFO

Belady's anomaly is the counter-intuitive result that giving a process more frames can increase the number of page faults, and FIFO is the standard example. LRU and the optimal algorithm are stack algorithms, and stack algorithms cannot suffer it.

Answer: A

Correct answer: elements

The individual items that make up a data structure are its elements. The structure is the arrangement; the elements are what it arranges.

Answer: B

Correct answer: object program

The output of a translator is the object program - the machine code or intermediate code produced from the source.

Answer: A

Correct answer: the cost incurred

Compaction works, but every byte of every process must be copied, and nothing else can run while it happens. That expense is its drawback.

Answer: B

Correct answer: addresses are bound at execution time

Compaction moves running processes to consolidate the free space, which means a process must be able to change its physical location while it is loaded. That is possible only where addresses are bound at execution time, through a relocation register or a page table that the operating system can simply update. Where binding happens at compile time or load time, a process’s addresses are fixed once and for all, and moving it would leave every reference pointing at the wrong place. The purpose of compaction is to cure external fragmentation, gathering scattered holes into one usable block. Its cost is heavy: every process must be copied, and the system can do nothing else meanwhile, so it is used sparingly. Under paging, compaction is unnecessary rather than required - the second option inverts the relation. Paging removes external fragmentation by definition, since any free frame serves for any page and physical contiguity is never needed. The technique survives in garbage-collected runtimes, which compact the heap for the same reason.