Memory Management Questions and Answers

Answer: A

Correct answer: page table

Each process has its own page table, which is what gives it a private address space: the same page number in two processes maps to different frames.

Answer: C

Correct answer: 100 Area: = Width*Length

COMAL keeps BASIC's line numbers but takes Pascal's assignment operator, so the statement carries both: the number 100 and the symbol :=. That mixture is exactly what COMAL was designed to be.

Answer: A

Correct answer: the number of partitions

One process per partition means the number of processes that can be in memory at once, and so the degree of multiprogramming, cannot exceed the number of partitions.

Answer: A

Correct answer: the page has been modified since it was loaded

The dirty or modify bit records whether a page has been written to since it was brought into memory. The hardware sets it on any write to the page. Its purpose is to avoid unnecessary disk writes. When a page is chosen for replacement, a clean page - one never modified - can simply be discarded, since an identical copy already exists on the backing store. A dirty page must be written out first. Since a disk write costs milliseconds, preferring clean victims measurably improves performance, and some replacement algorithms weigh the dirty bit alongside recency for exactly that reason. It sits among the other status bits in a page table entry: the valid bit, saying whether the page is resident; the reference bit, used by clock and second-chance algorithms to approximate LRU; and protection bits marking a page read-only or execute-only. Code pages are typically read-only and therefore always clean, which is one reason they are cheap to evict.

Answer: D

Correct answer: All of the above

All three are true of a firewall: it may be implemented in hardware or in software, it examines the traffic crossing a boundary, and what it does with each packet is decided by a configured set of rules.

Answer: C

Correct answer: Both 1 and 2

A firewall does both: it blocks traffic that should not reach the network at all, and it applies rules deciding which of the permitted traffic may reach which internal resources.

Answer: A

Correct answer: Paging to disk is often avoided so that timing is predictable

A real-time system is judged by whether it meets deadlines, not by average throughput, so predictability matters more than efficiency. Demand paging introduces a page fault whose cost is several milliseconds and whose occurrence cannot be predicted, which is intolerable where a response must be guaranteed within a bounded time. Such systems therefore either avoid paging altogether or allow critical pages and code to be pinned in memory - locked so the replacement algorithm cannot evict them. Many use fixed contiguous allocation, accepting the fragmentation in exchange for determinism. The same reasoning runs through the rest of the design: preemptive priority scheduling with bounded latency, priority inheritance to avoid unbounded priority inversion, and interrupt handlers kept short. The distinction is between hard real-time systems, where a missed deadline is a failure - flight controls, medical devices - and soft ones, where it merely degrades quality, as in video playback. Only the former forbids paging outright.

Answer: D

Correct answer: Switching hub

A switching hub, or switch, reads the destination address in each frame and forwards it only to the port where that address lies, instead of repeating it to every port as a plain hub does.

Answer: D

Correct answer: New

In C++ dynamic memory is obtained with the new operator and released with delete. malloc and calloc are C library functions, and unlike new they do not call a constructor.

Answer: C

Correct answer: segment length

The limit is the length of the segment, and every offset is checked against it before the address is formed.