Computer Operating System Questions and Answers

Answer: A

Correct answer: recognition of basic syntactic constructs through reductions

Syntax analysis takes the token stream and parses it against the grammar, reducing sequences of tokens to the constructs they form - expressions, statements, declarations - and reporting anything the grammar does not allow. Recognising the basic elements is lexical work, and improving the matrix is optimisation.

Answer: D

Correct answer: allows multiple programs to reside in separate areas of core at the same time

Multiprogramming keeps several programs in memory at once so that when one blocks for input or output the processor can turn immediately to another, which is what keeps an expensive processor busy. Dividing memory into pages and allocating processor time are the separate mechanisms it relies on.

Answer: D

Correct answer: All of the above

MS-DOS, OS/2 and UNIX are all operating systems - software that manages the processor, memory, files and devices and provides the interface programs run against. Each was a major system in its own market.

Answer: B

Correct answer: dispatch tasks according to execution characteristics

Multilevel feedback queues watch how each process behaves: one that uses its whole time slice is moved down to a lower-priority, longer-slice queue, while one that blocks early stays high. Interactive work therefore keeps its quick response and processor-bound work still makes progress, without anyone declaring in advance which is which.

Answer: D

Correct answer: Terminate Stay Resident

A TSR - terminate and stay resident - program returns to the DOS prompt but leaves itself in memory, usually hooked to an interrupt, so it can be summoned by a hot key or invoked by the hardware. Pop-up utilities and device drivers were written this way.

Answer: D

Correct answer: 128

The virtual address space is \( 2^{16} \) bytes and each page holds \( 0.5\ \text{KB} = 512 = 2^9 \) bytes, so the number of pages is \[ \frac{2^{16}}{2^{9}} = 2^{7} = 128 \] - the top 7 bits of the address are the page number and the low 9 bits the offset within it.

Answer: D

Correct answer: all of the above

The compile-and-go scheme suffers all three drawbacks: the translator itself occupies memory that the program being run could have used; the source must be retranslated every single time the program is run; and it offers no way to combine separately translated segments, so subroutines cannot be written in another language or shared.

Answer: B

Correct answer: DELTREE/F

DELTREE deletes a directory with everything beneath it and normally asks for confirmation first; the /F switch suppresses that prompt so the command can run unattended in a batch file.

Answer: B

Correct answer: RD

RD (RMDIR) removes a directory, and it will only do so if the directory is empty - a deliberate safeguard against deleting a tree by accident. MD creates a directory, and DEL and ERASE remove files.

Answer: A

Correct answer: directories

A disk is organised into directories - named groups of files, each of which may contain further directories, so the whole disk forms a tree from the root downwards. The tree keeps related files together and lets the same file name be used in different places.