50 Operating System MCQs with Answers

Question 31

Which of the following is NOT a valid deadlock prevention scheme? (GATE CS 2000)

• Release all resources before requesting a new resource
• Number the resources uniquely and never request a lower numbered resource than the last one requested.
• Never request a resource after releasing any resource
• Request and all required resources be allocated before execution.

Question 32

Consider the following proposed solution for the critical section problem. There are n processes: P0 ...Pn−1. In the code, function pmax returns an integer not smaller than any of its arguments. For all i, t[i] is initialized to zero. Which one of the following is TRUE about the above solution?

• At most one process can be in the critical section at any time
• The bounded wait condition is satisfied
• The progress condition is satisfied
• It cannot cause a deadlock

Question 33

An operating system contains 3 user processes each requiring 2 units of resource R. The minimum number of units of R such that no deadlocks will ever arise is

• 3
• 5
• 4
• 6

Question 34

Two shared resources R₁ and R₂ are used by processes P₁ and P₂. Each process has a certain priority for accessing each resource. Let T_ij denote the priority of P_i for accessing  R_j. A process P_i can snatch a resource R_h from process P_j if T_ik is greater than T_jk. Given the following :

1. T₁₁ > T₂₁
2. T₁₂ > T₂₂
3. T₁₁ < T₂₁
4. T₁₂ < T₂₂

Which of the following conditions ensures that P₁ and P₂ can never deadlock?  

• (I) and (IV)
• (II) and (III)
• (I) and (II)
• None of the above

Question 35

Which of the following commands or sequences of commands will rename a file x to file y in a Unix system? I. mv y, x II. mv x, y III. cp y, x (rm x) IV. cp x, y (rm x)

• II and III
• II and IV
• l and III
• II only

Question 36

The shell command

find -name passwd -print

is executed in /etc directory of a computer system running Unix. Which of the following shell commands will give the same information as the above command when executed in the same directory?  

• ls passwd
• cat passwd
• grep name passwd
• grep print passwd

Question 37

Consider the following statements : 

(a) UNIX provides three types of permissions 
* Read 
* Write 
* Execute 

(b) UNIX provides three sets of permissions 
* permission for owner 
* permission for group 
* permission for others 

Which of the above statement/s is/are true?

• only (a)

• only (b)

• Both (a) and (b)

• Neither (a) nor (b)

Question 38

The linux command “mknod myfifo b 4 16”

• Will create a character device if the user is root
• Will create a named pipe FIFO if the user is root
• Will create a block device if the user is root
• None of the above

Question 39

Unix command to change the case of first three lines of file “shortlist” from lower to upper

• $ tr ‘[a – z]’ ‘[A – Z]’ shortlist ¦ head-3
• $ head-3 shortlist ¦ tr ‘[a – z]’ ‘[A – Z]’
• $ tr head -3 shortlist ‘[A – Z]’ ‘[a – z]’
• $ tr shortlist head -3 ‘[a – z]’ ‘[A – Z]’

Question 40

Which of the following information about the UNIX file system is not correct?

• Super block contains the number of i-nodes, the number of disk blocks, and the start of the list of free disk blocks.
• An i-node contains accounting information as well as enough information to locate all the disk blocks that holds the file’s data.
• Each i-node is 256-bytes long.
• All the files and directories are stored in data blocks.