Computer Operating System Questions and Answers

Answer: A

Correct answer: preemptive scheduling

Under preemptive scheduling the operating system may take the processor from a process that is still able to run - when its time slice expires or a higher-priority process becomes ready - suspending it temporarily and resuming it later. Non-preemptive scheduling waits for the process to block or finish.

Answer: C

Correct answer: Terminal Table

The terminal table holds the fixed vocabulary of the language - its keywords, operators and punctuation, each with the information the compiler needs about it. It is a permanent database because it is the same for every program compiled, unlike the identifier and literal tables, which are built afresh from each source 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: C

Correct answer: which perform indicated operations on two fast registers of the machine

Register-to-register instructions take both operands from the processor’s own registers and leave the result in a register, so no memory access is needed and they are the fastest form. Storage-to-storage instructions work entirely in main memory, and register-to-storage instructions combine the two.

Answer: A

Correct answer: carelessness by users

The commonest security failure is not technical but human - passwords written down or shared, screens left unlocked, attachments opened, procedures bypassed for convenience. Technology can only limit the damage; the weakest point is almost always the person using the system.

Answer: C

Correct answer: EXE

.EXE marks an executable program - one with a relocation header, so it may exceed 64 KB and use several segments. .COM is the smaller single-segment form, .SYS a driver, and the others are not program files.

Answer: D

Correct answer: all of the above

Storage assignment reserves space for every variable the source program refers to, for the temporary locations the generated code needs to hold intermediate results, and for the literals - and it must ensure the storage is aligned to whatever boundary the machine requires. All three tasks belong to that phase.

Answer: B

Correct answer: 1

A critical section is code that touches a shared resource, and a race condition arises exactly when two processes are inside one at the same time. Mutual exclusion therefore admits at most one process at a time - which is why the guarding semaphore is initialised to 1.

Answer: B

Correct answer: to balance resource utilization

Admitting a mixture of jobs so that processor-bound and input/output-bound work run together keeps both the CPU and the devices busy instead of leaving one idle while the other saturates. That objective is balanced resource utilisation; fairness, priority and predictability are separate goals.

Answer: A

Correct answer: 1981

IBM shipped PC-DOS 1.0 with the original IBM Personal Computer in August 1981. Microsoft supplied it, having bought 86-DOS from Seattle Computer Products and adapted it, and sold the same system separately as MS-DOS.