Computer Operating System Questions and Answers

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: 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.

Answer: A

Correct answer: time sharing

Time sharing gives each user a short slice of processor time in rapid rotation. Because a slice comes round again in a fraction of a second, and human reaction is far slower, each user has the impression of a machine to themselves.

Answer: B

Correct answer: requires detailed system performance information

Capacity planning forecasts whether the installation will meet its service targets as the workload grows, and that forecast can only be built on measured data - processor and device utilisation, queue lengths, response times, paging rates. It depends heavily on the monitoring tools available, and small installations need it too.

Answer: D

Correct answer: Any of the above

Response time suffers wherever the bottleneck lies. A saturated processor leaves work queuing for the CPU; a high input/output rate leaves it queuing for a device; a high paging rate leaves it queuing for memory. Any one of them alone will lengthen response times.

Answer: B

Correct answer: is less secure than end-to-end encryption

Link encryption protects each hop separately, so the message is decrypted and re-encrypted at every intermediate node - and lies in clear inside each of them. End-to-end encryption keeps it encrypted the whole way, so the intermediate nodes never see the plaintext at all.

Answer: B

Correct answer: multi threading

Multithreading lets one program contain several independent threads of control, which may be scheduled onto different processors and so be genuinely active at the same time, while sharing the program’s address space. Multiprogramming is about several separate programs rather than several threads within one.

Answer: B

Correct answer: Literal table

The literal table records every constant appearing in the source - numbers, strings, character constants - so that each can be assigned storage once and referenced from wherever it occurs. It is built during lexical analysis, along with the identifier table, and is different for every program.

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: A

Correct answer: absolute mode

In absolute (direct) addressing the instruction carries the actual address of the operand, so one memory access fetches the value. Immediate addressing carries the value itself, and indirect addressing carries the address of a location that in turn holds the address.