Computer Operating System Questions and Answers

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.

Answer: B

Correct answer: linking loader

A linking loader takes the separately compiled object modules, resolves the external references between them, relocates their addresses to the area of memory they are to occupy, and loads the result ready to run - combining linking and loading in one pass.

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: D

Correct answer: it’s a CD-ROM DOS driver

MSCDEX.EXE is the Microsoft CD-ROM Extensions: loaded from AUTOEXEC.BAT, it gives the CD-ROM a drive letter and supplies the file system for it, working with the hardware driver loaded earlier from CONFIG.SYS.

Answer: D

Correct answer: Preemption

The four Coffman conditions are mutual exclusion, hold and wait, no preemption and circular wait, and all four must hold at once. Preemption is the opposite of the third condition, so allowing it prevents deadlock rather than causing it.

Answer: B

Correct answer: ATTRIB + r CBT.EXE

ATTRIB +R sets the read-only attribute, after which the file cannot be changed or deleted until the attribute is cleared with ATTRIB -R. RENAME, COPY and MODE do not alter file attributes.

Answer: C

Correct answer: Used for address translation

The page map table holds one entry per virtual page, giving the frame it currently occupies together with its valid, referenced and modified bits. The memory management unit consults it on every reference to turn a virtual address into a physical one.

Answer: C

Correct answer: there is no need for an address i.e. the data is used as an address

Associative or content-addressable memory is searched by content rather than by location: a pattern is presented and every cell compares itself with it simultaneously, returning the matching entry in one cycle. It is what makes a translation lookaside buffer and a cache tag store fast enough to be useful.