System Calls GATE CS PYQ Quiz

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Question 1

A process executes the code

fork();
fork();
fork();

The total number of child processes created is

Question 2

A process executes the following code

for (i = 0; i < n; i++) fork();

The total number of child processes created is

n
2ⁿ - 1
2ⁿ
2⁽ⁿ⁺¹⁾ - 1

Question 3

The time taken to switch between user and kernel modes of execution be t1 while the time taken to switch between two processes be t2. Which of the following is TRUE?

t1 > t2
t1 = t2
t1 < t2
nothing can be said about the relation between t1 and t2

Question 4

Which of the following standard C library functions will always invoke a system call when executed from a single-threaded process in a UNIX/Linux operating system?

exit
malloc
sleep
strlen

Question 5

A CPU generally handles an interrupt by executing an interrupt service routine

As soon as an interrupt is raised
By checking the interrupt register at the end of fetch cycle.
By checking the interrupt register after finishing the execution of the current instruction.
By checking the interrupt register at fixed time intervals.

Question 6

A computer handles several interrupt sources of which the following are relevant for this question.


. Interrupt from CPU temperature sensor (raises interrupt if 
  CPU temperature is too high)
. Interrupt from Mouse(raises interrupt if the mouse is moved 
  or a button is pressed)
. Interrupt from Keyboard(raises interrupt when a key is 
  pressed or released)
. Interrupt from Hard Disk(raises interrupt when a disk 
  read is completed)

Which one of these will be handled at the HIGHEST priority?

Interrupt from Hard Disk
Interrupt from Mouse
Interrupt from Keyboard
Interrupt from CPU temperature sensor

Question 7

Which one of the following is true for a CPU having a single interrupt request line and a single interrupt grant line?

Neither vectored interrupt nor multiple interrupting devices are possible.
Vectored interrupts are not possible but multiple interrupting devices are possible.
Vectored interrupts and multiple interrupting devices are both possible.
Vectored interrupt is possible but multiple interrupting devices are not possible.

Question 8

Consider the following code fragment:

  if (fork() == 0)
  { a = a + 5; printf(“%d,%d\\n”, a, &a); }
  else { a = a –5; printf(“%d, %d\\n”, a, &a); }

Let u, v be the values printed by the parent process, and x, y be the values printed by the child process. Which one of the following is TRUE?

u = x + 10 and v = y
u = x + 10 and v != y
u + 10 = x and v = y
u + 10 = x and v != y

Question 9

Consider the following statements with respect to user-level threads and kernel supported threads

 
i.   context switch is faster with kernel-supported threads
ii.  for user-level threads, a system call can block the 
     entire process
iii. Kernel supported threads can be scheduled independently
iv.  User level threads are transparent to the kernel

Which of the above statements are true?

(ii), (iii) and (iv) only
(ii) and (iii) only
(i) and (iii) only
(i) and (ii) only

Question 10

The following C program is executed on a Unix / Linux system:

#include <unistd.h>
  int main() {
    int i;
    for (i = 0; i < 10; i++)
      if (i % 2 == 0) fork();
    return 0;
  }

The total number of child process created is __________ .

Note -

This was Numerical Type question.

Tags:

Operating Systems

GATE CS

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