Interview Questions in Operating Systems

Following are a few basic questions that cover the essentials of OS:


1.      Explain the concept of Reentrancy.

It is a useful, memory-saving technique for multiprogrammed timesharing systems. A Reentrant Procedure is one in which multiple users can share a single copy of a program during the same period. Reentrancy has 2 key aspects: The program code cannot modify itself, and the local data for each user process must be stored separately. Thus, the permanent part is the code, and the temporary part is the pointer back to the calling program and local variables used by that program. Each execution instance is called activation. It executes the code in the permanent part, but has its own copy of local variables/parameters. The temporary part associated with each activation is the activation record. Generally, the activation record is kept on the stack.

Note: A reentrant procedure can be interrupted and called by an interrupting program, and still execute correctly on returning to the procedure.


2.      Explain Belady's Anomaly.

Also called FIFO anomaly. Usually, on increasing the number of frames allocated to a process' virtual memory, the process execution is faster, because fewer page faults occur. Sometimes, the reverse happens, i.e., the execution time increases even when more frames are allocated to the process. This is Belady's Anomaly. This is true for certain page reference patterns.


3.      What is a binary semaphore? What is its use?

A binary semaphore is one, which takes only 0 and 1 as values. They are used to implement mutual exclusion and synchronize concurrent processes.

For complete set of questions refer to the attachment below.


Comments (25)

Said this on 4-26-2008 At 09:02 pm
This site is excellent. You people are doing a great job. Heads up.
Said this on 4-28-2008 At 04:32 pm
Said this on 4-29-2008 At 05:16 pm
very nice
santosh goud
Said this on 5-5-2008 At 12:18 pm
Hi i'm trying for tech support job.
i hope that this article is helpful for me.
Said this on 5-13-2008 At 01:56 am
raja mukherjee
Said this on 5-13-2008 At 10:06 am
Excellent.It help me a lot
Said this on 5-15-2008 At 11:08 pm
it really helpful to us
Said this on 5-24-2008 At 07:11 am
it is very good to understand pattern of interviews
Said this on 5-25-2008 At 03:19 am
i want cts interview question paper
Said this on 6-2-2008 At 10:54 pm
i am a programmer doing Master in Computer Science. i liked site the most.
Said this on 6-13-2008 At 10:33 pm
Said this on 7-17-2008 At 01:24 am
this site is fantastic...thanx to evry1
Said this on 7-17-2008 At 10:42 am
Very usefull for me
sukanya das
Said this on 7-25-2008 At 12:17 pm
its a helpful site
Said this on 7-27-2008 At 04:38 pm
good but need more quantity
Said this on 7-27-2008 At 07:54 pm
baljit singh
Said this on 9-14-2008 At 07:40 am
thanks for this
Said this on 9-17-2008 At 07:37 am
studty doesn't complete.
Said this on 9-17-2008 At 01:52 pm
life is live
Said this on 7-15-2009 At 05:40 pm
very very thanks
Said this on 8-16-2009 At 11:32 pm
.....good man
Said this on 8-24-2009 At 11:01 am
Good Job
Said this on 9-7-2009 At 12:21 am
is good
Said this on 9-12-2009 At 05:51 pm
Superb.... material. Good work guys
Said this on 11-2-2009 At 09:28 pm

Congratulations team...I think you are doing a wonderful job of mainitaining this site for a lot of guys who are preparing for interviews....The content is the ultimate specially unix related....Thanks a lot....

Post a Comment
* Your Name:
* Your Email:
(not publicly displayed)
Reply Notification:
Approval Notification:
* Security Image:
Security Image Generate new
Copy the numbers and letters from the security image:
* Message:

Email to Friend

Fill in the form below to send this article to a friend:

Email to Friend
* Your Name:
* Your Email:
* Friend's Name:
* Friend's Email:
* Security Image:
Security Image Generate new
Copy the numbers and letters from the security image
* Message: