Computer Operating System Questions and Answers

Answer: A

Correct answer: reenterable

A reentrant program keeps no modifiable data in its own code area, so one copy in memory can be executing on behalf of several users at once, each with its own stack and work area. That is exactly what is wanted of a compiler or an editor on a shared system.

Answer: B

Correct answer: 26

Drives are named by letters, so DOS can address 26 of them, A to Z - A and B being reserved for diskette drives and C onwards for hard disks, network drives and CD-ROMs.

Answer: B

Correct answer: UNIX

UNIX was written at Bell Labs from 1969 by Ken Thompson and Dennis Ritchie for their own use, and its design shows it: small tools that do one thing, combined through pipes, with a hierarchical file system and everything treated as a file. It spread through universities before it ever became a commercial product.

Answer: D

Correct answer: real time systems generally use non-preemptive CPU scheduling

A real-time system must be able to take the processor away from a running task the instant a more urgent one becomes ready, so it uses preemptive scheduling - making that statement false. The other three are true: preemption means the CPU can be taken from a running process, time-sharing systems rely on it, and it makes response times more predictable.

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.

Answer: D

Correct answer: faster

A disk beats main memory on every count listed except speed: it keeps its contents without power, holds far more, and costs far less per bit. But an access takes milliseconds against the nanoseconds of memory - a difference of about a million times, which is why data must be brought into memory to be worked on.

Answer: B

Correct answer: Ctrl+Alt+DEL

Ctrl + Alt + Del restarts DOS without switching the power off - a warm boot, which skips the memory test and much of the hardware initialisation and so comes back much sooner than a cold start.

Answer: D

Correct answer: all of the above

A macro processor for assembly language may be built in any of the three ways: as an independent two-pass processor, as an independent one-pass processor, or incorporated into pass 1 of the assembler itself. The last saves a scan of the source and shares the assembler’s tables, at the cost of a more complex pass.

Answer: C

Correct answer: gives each task the same chance at the processor

Round robin gives every ready process the same fixed time slice in turn, and a process still running when its slice expires goes to the back of the queue. It is simple to implement and scrupulously fair, but it takes no account of whether a task is interactive or processor-bound.

Answer: B

Correct answer: immediate mode

In immediate addressing the operand itself is written into the instruction, so no memory access is needed to fetch it - the value travels with the instruction. It is how constants are supplied, as in ADD #5.