Computer Operating System Questions and Answers

Answer: A

Correct answer: the collection of pages that a process accesses

The working set of a process is the set of pages it has referenced in the recent past, taken as a prediction of what it will need next. Keeping a process’s whole working set resident stops it faulting continually, and refusing to run a process whose working set will not fit is how thrashing is prevented.

Answer: C

Correct answer: A collection of software routines

An operating system is software: a body of routines that manage the processor, memory, files and devices, and present them to programs through system calls. It runs on the hardware and controls the input and output devices, but is neither of them.

Answer: D

Correct answer: all of the above

VSAM offers three file organisations: the entry-sequenced data set, where records are held in the order written; the key-sequenced data set, indexed on a key; and the relative record data set, addressed by record number. All three are components of the VSAM file organisation.

Answer: B

Correct answer: Public domain program

A public domain program carries no copyright restriction, so anyone may compile, use, change and redistribute it freely. Shareware is copyrighted and may be tried before purchase but must then be paid for, and firmware describes where a program is stored rather than its licence.

Answer: D

Correct answer: with the least processor needs

Shortest job first selects the ready process with the smallest expected processor burst. That minimises the average waiting time - provably so - but it needs an estimate of each burst in advance and can starve long jobs indefinitely if short ones keep arriving.

Answer: C

Correct answer: worst fit

Worst fit deliberately places a request in the largest free hole, on the reasoning that the remainder left over will still be big enough to be useful, whereas best fit leaves a scatter of slivers too small for anything. First fit simply takes the first hole large enough.

Answer: D

Correct answer: disk

A block device transfers data in fixed-size blocks and can be addressed randomly - any block read or written directly, which is why file systems are built on them. A mouse, a printer and a terminal deliver or accept a stream of characters, so they are character devices.

Answer: A

Correct answer: program structure

Thrashing sets in when processes fault continually because their working sets do not fit, and how tightly a program’s references cluster - its locality, which follows from its structure - decides how large that working set is. A program that scans a large array against the page order can thrash where a well-structured one of the same size will not.

Answer: C

Correct answer: operating environment

An operating environment is a layer placed over the operating system to make it easier to use - a menu shell or a graphical environment such as early Windows over MS-DOS - presenting the same facilities in a friendlier form. Timesharing and multitasking are things the operating system does, not aids to using it.

Answer: D

Correct answer: all of the above

Assembly language improves on machine language in all three ways: the operation codes are mnemonics that can be read, addresses are written as symbolic labels that the assembler resolves, so inserting an instruction does not renumber everything after it, and constants and data areas can be declared directly rather than hand-encoded.