Memory Management Questions and Answers

Answer: D

Correct answer: mnemonics

Using fixed short words such as ADD and JMP in place of binary operation codes is the technique of mnemonics, and it is what assembly language consists of.

Answer: B

Correct answer: string variable

NAMEINR holds whatever name has been read, so its value changes as the program runs. That makes it a string variable, as against the fixed "***" it is compared with.

Answer: C

Correct answer: to protect the address spaces of processes

The relocation register holds the smallest physical address a process may use and the limit register the size of its range. Every address is checked against the limit and then added to the relocation value, so a process cannot reach outside its own space.

Answer: A

Correct answer: TLB miss

A page number not found in the TLB is a TLB miss, and the page table in memory must then be consulted; the entry is usually added to the TLB afterwards.

Answer: A

Correct answer: split into halves and merged with their partner when freed

The buddy system keeps memory in blocks whose sizes are powers of two. A request is satisfied by repeatedly halving a block until the smallest adequate size is reached; the two halves produced at each split are buddies. When a block is freed, the system checks whether its buddy is also free, and if so merges the pair back into the larger block, repeating upward. Its merit is that coalescing is fast. A block’s buddy is found by flipping a single bit of its address, so merging costs almost nothing - unlike a general free-list, where finding an adjacent free block requires searching. Its cost is internal fragmentation: a request for 33 KB receives 64 KB, wasting nearly half. On average about a quarter of allocated memory is lost. It is used in the Linux kernel for physical page allocation, where the fixed page size limits the waste, and the slab allocator is layered on top of it to serve small kernel objects efficiently.

Answer: A

Correct answer: frames

Physical memory is divided into fixed-size frames and logical memory into pages of the same size. Keeping the two names apart is what makes the rest of paging describable.

Answer: A

Correct answer: Computers can share information and share peripheral equipment

A LAN allows files and devices to be shared. It does not make any individual machine faster, and reaching the internet requires a further connection beyond the local network.

Answer: A

Correct answer: narrative

REM introduces a remark in BASIC - text the interpreter ignores, included for the reader. Such text is the program's narrative.

Answer: D

Correct answer: CLOSED function

Marking a COMAL procedure CLOSED makes its variables local to it, so nothing inside can disturb the rest of the program. That is COMAL's way of enforcing what Pascal gets from block scope.

Answer: D

Correct answer: the page is in the process’s address space and currently in memory

The valid-invalid bit records whether a page-table entry refers to a page that is legally part of the process’s address space and currently resident in physical memory. Marked invalid, any reference to it traps to the operating system. The trap has two possible meanings, and the operating system must distinguish them. Either the reference is genuinely illegal - outside the address space - in which case the process is terminated with an addressing error; or the page is legal but not resident, in which case it is a page fault and the page is brought in from the backing store. The kernel keeps a separate record of which pages a process is entitled to in order to tell the two apart. The other bits in an entry serve different purposes: the dirty bit records modification, so a clean page need not be written back; the reference bit supports clock and second-chance replacement; and protection bits mark a page read-only or execute-only. Demand paging works by starting every page marked invalid.