Gate Questions Set-1

GATE-1992

1. At a particular time of computation the value of a counting semaphore is 7.

    Then 20 P operations and 15 V operations were completed on this

    semaphore. The resulting value of the semaphore is:

(a) 42 (b) 2 (c) 7 (d) 12

Ans:- Option - B

Explanation:- 

The wait operation (P) decrements the semaphore value.

The Signal operation(v) increments the semaphore value.

The 20 P operation will decrements the semaphore value 20 times.

The 15 V operation will increments the semaphore value 15 times.

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GATE-1992

2. A computer system has 6 tape drives, with n process completing for them.

Each process may need 3 tape drives. The maximum value of n for which the

system is guaranteed to be deadlock free is:

(a) 2 (b) 3 (c) 4 (d) 1

Ans:-Option-A

Explanation:- 

Deadlock:- 

                   Deadlock is a situation in which two or more competing actions are each waiting for the other to finish, and thus neither ever does. Read more

Lets check with maximum value that is option c

suppose process 1==> 2 tape drives

            process 2==>  2 tape drives

            process 3==>  1 tape drive

            process 4==>  1 tape drive

in this situation process 1 waiting for other processes to be free. and same way process 2 waiting for process 2 waiting for other processes to be free. so deadlock will occur.

Lets check option B

Process 1==> 2 tape drives.

Process 2==> 2 tape drives.

Process 3==> 2 tape drives.

Here also one process waiting for other process to release resources. so deadlock will occur.

now check Option A

Process 1==> 3 tape drives.

Process 2==> 3 tape drives.

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GATE-1992

3. Which of the following is an example of a spooled device?

(a) The terminal used to the input data for a program being executed.

(b) The secondary memory device in a virtual memory system

(c) A line printer used to print the output of a number of jobs.

(d) None of the above

Ans:- Option-C

Explanation:-

Spool means simultaneous peripheral operations on-line.

The common spooling application is print spooling:

Generally Printers typically can print only a single document at a time and require seconds or minutes to do so. With spooling application, multiple processes can write documents to a print queue without waiting. As soon as a process has written its document to the spool device, the process can perform other tasks, while a separate printing process operates the printer.

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GATE-1993

1. Consider a system having m resources of the same type. These resources are shared by 3 processes A, B and C, which have peak demands of 3, 4 and 6 respectively. For what value of m deadlock will not occur?

       (a)7 (b) 9 (c) 10 (d) 13 (e) 15

Ans:- Option-D

Explanation:-

Lets start with option-A

Process A ==> 2 resources 

Process B ==> 3 resources 

Process C ==> 2 resources

In this situation one process will wait for other processes to be free. so deadlock occur.

Option- B

Process A ==> 2 resources 

Process B ==> 3 resources 

Process C ==> 4 resources      
Deadlock.

Option-C

Process A ==> 2 resources 

Process B ==> 3 resources 

Process C ==> 5 resources

Option D

Process A ==> 3 resources 

Process B ==> 4 resources 

Process C ==> 6 resources

So it will be deadlock free.

Note: Also option E is also possible.

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GATE-1993

2. Assume that the following jobs are to be executed on a single processor system

Job_id	Burst time
P	4
Q	1
R	8
S	1
T	2

The jobs are assumed to have arrived at time 0 and in the order p, q, r, s, t.

Calculate the departure time (completion time) for job p if scheduling is 

round robin with time slice 1   

(a)  4  (b) 10 (c) 11 (d) 12 (e) None of the above

Ans:- option-C

Explanation:-