Computer Operating System Questions and Answers

Answer: C

Correct answer: creation of more optimal matrix.

Improving the intermediate representation - removing common subexpressions, hoisting loop-invariant code, folding constants - is done before any target machine is considered, so it belongs to machine-independent optimisation. Register allocation and instruction selection depend on the machine and come later.

Answer: D

Correct answer: inquires to see if a terminal has any transaction to send

Polling is the controller asking each device or terminal in turn whether it has anything to send, and moving on if it has not. It costs processor time whether or not there is work, which is why interrupts are preferred where the hardware supports them.

Answer: B

Correct answer: BAT

A batch file carries the extension .BAT, and DOS recognises it as a list of commands to be executed one after another rather than as machine code. COM and EXE hold executable programs, and SYS holds device drivers and system files.

Answer: D

Correct answer: is waiting for some temporarily unavailable resources

A blocked process is waiting for something that is not yet available - the completion of an input operation, or a semaphore held elsewhere. It is not executable and does not belong in the run queue: the scheduler will not consider it again until the event it waits for occurs and moves it back to ready.

Answer: B

Correct answer: DISKCOMP

DISKCOMP compares two diskettes track by track and sector by sector, reporting where they differ - the usual check after a DISKCOPY. DISKCOPY duplicates a disk rather than comparing.

Answer: C

Correct answer: only the active pages of a program are stored in primary storage

Virtual storage keeps only the pages a program is currently using in main memory and leaves the rest on disk, fetching each as it is referenced. A program can therefore be larger than the memory available, and the memory can be shared among more programs than would otherwise fit.

Answer: D

Correct answer: all of the above

Building the macro processor into pass 1 of the assembler avoids implementing input, output and table handling twice, avoids writing an intermediate file between the two programs, and gives the programmer more flexibility, since macro definitions and assembler statements may be interleaved freely. All three advantages follow from the merge.

Answer: B

Correct answer: 2

Dekker’s algorithm was the first correct software solution to mutual exclusion, and it works for exactly two processes. It combines two intention flags with a turn variable, so that when both want to enter the turn variable breaks the tie and neither can be starved. Generalising it to \( n \) processes needed Dijkstra’s and later Lamport’s work.

Answer: C

Correct answer: allows each program in turn to use the memory

Swapping moves a whole process out to backing store and brings another in, so the processes take turns occupying memory rather than sharing it at the same instant. It is the coarsest form of memory management, and it is what paging refines by moving pages rather than whole processes.

Answer: C

Correct answer: Program

A program is the sequence of instructions, written in a computer language, that produces the desired result when executed. An algorithm is the method it implements, expressed independently of any language, and a decision table sets out conditions and actions as a design document.