MCQs Operating System Lab 80+

1. Input string is 987654321!@#$%^&*()abcdefghij

int main() 
{ 
int x,y,z; 
char b[50]; 
 
x=open("file.txt",O_RDWR); 
y=lseek(x,10,SEEK_SET); 
read(x,b,15); 
write(1,b,20);
} 

The output of the program is:

• @#$%^&*()abcdef
• @#$%^&*()abcdefghij
• Open Error
• @#$%^&*()

Ans: A

2. How many times hello will be printed?

#include<stdio.h> 
 
#include<sys/types.h> 
 
int main() 
 
{ 
 
Pid_t p; 
 
printf("hello"); 
 
Fork(); 
 
Fork(); 
 
Fork(); 
 
printf("hello"); 
}

• 16
• 4
• 8
• 32

Ans: C

3. Choose the correct configuration

• B–>D–>A–>C
• A–>C–>B–>D
• D–>B–>A–>C
• B–>C–>A–>D

Ans: A

4. Which of the following statement is correct?

• pipe() creates a unidirectional stream having two descriptors.
• popen() creates a unidirectional stream having two descriptors.
• popen() creates a bidirectional stream having one descriptors.
• pipe() creates a bidirectional stream having two descriptors.

Ans: A

5. IPC stands for

• Inter process communication
• Inter personal communication
• Internal process connection
• Internal process communication

Ans: A

6. Which command is used to display the present working directory?

• pwd
• Whoami
• ls -l
• kernel

Ans: A

7. A file named “test.txt” already exists in your system. Which of the following syntax will be used to create new file “test1.txt ” for writing purposes?

• open(“test1.txt”, O_READ);
• open(“test1.txt”, O_RDONLY);
• open(“test1.txt”, O_CREAT|O_WRONLY, 0732);
• open(“test1.txt”, O_CREATE|O_RDWR);

Ans: C

8. To check the zombie process which of the following commands will be used?

• ./a.out & +ps
• ./a.out + ps
• ./a.out +ls
• ./a.out & + pwd

Ans: B

9. Choose the correct statement:

• Wait and signal operations are part of semaphores
• Wait and signal operations are part of inter process communication.
• Wait and signal operations are part of mutex lock.
• Wait and signal operations are part of threads.

Ans: A

10. The input in file is 987654321!@#$%^&*()abcdefghij

int main() 
 
{ 
 
int x,y,z; 
 
char b[50]; 
 
x=open("file.txt",O_RDWR); 
 
y=lseek(x,-11,SEEK_END); 
 
read(x,b,20); 
 
write(1,b,12);  
 
} 

The output of program is

• ()abcdefgh
• ()abcdefghij
• abcdefghij
• error in program

Ans: B

11. Mkfifo() creates the pipes by default in

• Unblocking mode
• Reading and writing mode
• Blocking mode
• Bidirectional mode

Ans: C

12. If exec is called immediately after forking __

• The program specified in the parameter to exec will replace the entire process
• All the threads will be duplicated
• All the threads may be duplicated
• None of the mentioned

Ans: A

13. A parent process calling _ system call will be suspended until children processes terminate.

• wait
• fork
• exit
• exec

Ans: A

14. Which of the following statement is false:

• msgget() function is used to get the data from message queue.
• msgctl() is a message queue control function.
• Msgget() is used to create and access a message queue.
• All of the above.

Ans: D

15. The third parameter of pthread_create() function is

• Name of the function which thread will execute
• Id of the thread.
• Attributes of the thread.
• Input to the function in the third parameter.

Ans: A

16. Which of the following statement is true?

• Pipe() creates unidirectional two pipes in which first is used for writing and second for reading.
• Pipe() creates unidirectional two pipes in which first is used for read and second for writing.
• Pipe() creates bidirectional one pipes which is used for reading and writing.
• popen() creates unidirectional two pipes in which first is used for read and second for writing.

Ans: A

17. The output is

int main() 
{ 
pid_t q; 
q=fork(); 
if(q==0) 
    { 
     printf("students"); 
      } 
else 
{ 
 printf("CSE LPU"); 
sleep(15); 
}
}

• CSE defunct LPU
• CSE LPU defunct students
• students CSE LPU
• studentsCSE LPU

Ans: D

18. The second parameter of pthread_create() function is

• Name of the function which thread will execute
• Id of the thread.
• Attributes of the thread.
• Input to the function in the third parameter.

Ans: C

19. Which of the following command opens the pipe in writing mode?

• popen(‘wr’,”wc –c”);
• popen(‘wc –c’,’w’);
• popen(‘wc’,’wr’);
• popen(“w+”,”wc –c”);

Ans: B

20. The output of given program is:

int main() 
{ 
char a[25]; int b; 
 
read(0,a,15); 
 
write(1,a,8); 
 
//printf("The output is %d\n",b); 
} 

Consider input as:1112131415

What will be the output?

• -1
• 012131415
• 11121314
• 1112131

Ans: C

21. The purpose of creating IPC_CREAT in shmget() is:

• to create a file
• to create a pipe
• to create a shared memory segment
• none of the mentioned

Ans: C

22. In the system table the process in the below snapshot with is known as:

Ans: Zombie Process

23. Choose the correct description of process management:

Call                             Description
a) p=lseek(fd,offset,whence)     1) Open file reading writing or both
b) S=stat(name, &buff)           2) Read data from file to buffer
c) a=open(file, flag, mode)      3) Write data fom a buffer into a file
d) a=write(fd, buffer,nbytes)    4) Move the file pointer
e) b=read(fd, buffer,nbytes)     5) Get a file status information

Ans: a->4, b->5, c->1, d->3, e->2

Operating System Lab Study Material

https://dextutor.com/courses/operating-system-programs/

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