Memory Management Questions and Answers

Answer: D

Correct answer: common algorithmic language

COMAL is COMmon ALgorithmic Language, devised in Denmark to give BASIC the structure of Pascal.

Answer: B

Correct answer: directive

A directive instructs the assembler itself - where to place code, how much storage to reserve - rather than producing an instruction for the processor to execute.

Answer: D

Correct answer: all of the above

Comments serve all three purposes: recording what a variable holds, what a module does, and marking where one section of the program ends and the next begins.

Answer: A

Correct answer: less than

A logical address is an offset from the start of the process, so it is valid only while it is less than the limit. An address equal to the limit is the first one beyond the region.

Answer: A

Correct answer: procedure

Both COMAL and Pascal call a named, callable block a procedure. A function is the variety that returns a value.

Answer: A

Correct answer: The process state, program counter and register contents

The Process Control Block is the data structure the operating system keeps for each process. It holds the process state - new, ready, running, waiting or terminated - the program counter, the contents of the CPU registers, scheduling information such as priority, memory management information including base and limit registers or page table pointers, accounting data, and the list of open files and allocated devices. Its purpose is to make a context switch possible. When the scheduler suspends a process, the entire CPU state is saved into its PCB; when it resumes, the state is restored and execution continues as though nothing had happened. Without that saved state, a process could never be interrupted. The PCB is also what a context switch costs: saving and restoring it is pure overhead, doing no useful work, which is why switching too often degrades throughput. It is sometimes called the task control block, and the collection of them is the process table.

Answer: A

Correct answer: operating system

Main memory holds the resident part of the operating system and the user processes together, and the question asks which of them it accommodates. The CPU is not in memory at all, so it cannot be part of the answer.

Answer: C

Correct answer: bits in each page table entry marking a page read-only or invalid

Protection is enforced through bits in the page table entry. Each entry carries a valid bit, saying whether the page belongs to the process’s address space at all, and permission bits marking it read-only, read-write or execute-only. The hardware checks these on every access and traps to the operating system on a violation. The mechanism is cheap because the page table must be consulted for translation in any case, so the check costs nothing extra. It also provides isolation at no additional cost: a process can only name addresses through its own page table, so it simply cannot express an address in another process’s memory. That is the foundation of process separation in every modern operating system. The no-execute bit, added to mainstream processors in the 2000s, is a security refinement of the same idea: marking data pages non-executable defeats a large class of attacks that inject code into a buffer and jump to it. Sharing is arranged by mapping the same frame into two page tables with different permissions.

Answer: A

Correct answer: File server

A file server holds programs and data centrally so that every user on the LAN can reach the same copy. A print server shares a printer and a communication server shares a link, neither of which is about sharing programs and data.

Answer: D

Correct answer: portable program

A program that runs on different machines after only small changes is portable. Portability is a property of the source rather than of any one compiled version.