Computer Operating System Questions and Answers

Answer: A

Correct answer: is usually the primary user interface

The command interpreter - the shell - is what the user actually talks to: it reads each command, finds the program that implements it, and runs it. It accepts free-format lines rather than fixed ones, and is a program like any other, which is why a system can offer several.

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: is necessary on all systems, regardless of how good

Every system needs maintenance, however well it was written: faults surface in use, the environment and the hardware change, the law and the business rules change, and users ask for more. Maintenance typically consumes the larger part of a system’s total cost over its life.

Answer: B

Correct answer: A FORTRAN program, written for the IBM-PC, is totally different from a FORTRAN program written for execution on the SUN machine

FORTRAN is a standardised high-level language, so the same source compiles and runs on both machines with little or no change - which is precisely the point of a high-level language. That statement is therefore the untrue one; the others are correct.

Answer: A

Correct answer: creates a load module

A linker takes the object modules produced by the translator, resolves the external references between them, and combines them into one load module ready for the loader to place in memory. It is needed whenever a program is built from more than one separately compiled part.

Answer: C

Correct answer: consists of a full or partial list of the token's as they appear in the program. Created by Lexical analysis and used for syntax analysis and interpretation

The uniform symbol table is the token stream: as the lexical phase recognises each element of the source it appends a uniform-length entry describing it, and the syntax phase then parses that list rather than the raw characters. It is built afresh for every program.

Answer: A

Correct answer: best fit

Best fit searches the free list for the smallest hole large enough, so the least space is wasted on this allocation. The drawback is that the remainders it leaves are tiny and unusable, so external fragmentation builds up over time.

Answer: D

Correct answer: index mode

In index addressing the effective address is the constant in the instruction plus the contents of the index register, so the constant names the start of an array and the register selects the element. Stepping the register walks through the array without changing the instruction.

Answer: D

Correct answer: Upward compatibility

Upward compatibility means a later version still runs what was written for the earlier ones, so users can move to the new system without abandoning their existing programs. It constrains the designers, but without it few would upgrade.

Answer: A

Correct answer: JCL

Special forms, and the printer they are to be mounted on, are described to the operating system in the job’s job control language statements - the DD statement naming the form number, so the operator is prompted to mount it before the job prints.