Computer Operating System Questions and Answers

Answer: B

Correct answer: Shareware

Shareware is distributed freely so that it can be tried, on the understanding that a fee is paid if it is kept and used. It remains copyrighted - which distinguishes it from public domain software, where the author has given up that claim altogether.

Answer: A

Correct answer: CD

CD changes the current directory, and CHDIR is simply its longer spelling - the same command under two names. MOVE relocates files rather than changing where you are.

Answer: A

Correct answer: synchronize critical resources to prevent deadlock

A semaphore is an integer with atomic wait and signal operations, used to guard a shared resource so that processes take it in a disciplined order. Used correctly - every process taking the semaphores in the same order - it both enforces mutual exclusion and prevents the circular waiting that would otherwise deadlock them.

Answer: D

Correct answer: all of the above

The producer–consumer problem needs mutual exclusion on the buffer and a way to make the producer wait when it is full and the consumer wait when it is empty. Semaphores provide both directly, event counters do it without mutual exclusion by counting occurrences, and monitors package the buffer with its condition variables. All three solve it.

Answer: A

Correct answer: are legitimate programs that allow unauthorized access

A Trojan horse works precisely because it appears to be a legitimate, useful program: the user installs and runs it willingly, and while it does whatever it advertises it also opens a way in for the attacker. Unlike a virus it does not replicate; its whole method is the disguise.

Answer: B

Correct answer: TYPE REPORT.TXT > PRN

> redirects standard output, and PRN is the DOS device name for the standard printer, so TYPE REPORT.TXT > PRN sends the file’s contents there instead of to the screen. The pipe symbol feeds output into another program, and PRN is a device, not a program.

Answer: A

Correct answer: Interpreter generates an object program from the source program

An interpreter produces no object program at all: it analyses and executes each statement as it reaches it, which is why a statement inside a loop is analysed afresh on every iteration. The other statements are true - it is a kind of translator, and it does re-analyse each statement every time.