GATE CS 2026 Set 1 Q.63: Processes, Threads and System Calls

Consider the following program snippet. Assume that the program compiles and runs successfully. Further, assume that the fork() system call is always successful in creating a process.

int main () {
   int i;
   for (i = 0; i < 3; i++){
      if (fork() == 0){
        continue;
      }
      break;
   }
   printf("Hello!");
   return 0;
}

The total number of times that the printf statement gets executed is ________. (answer in integer)

Your answer

Official answer and solution

Official answer: 4
From: Official GATE 2026 answer key

Solution

Trace the control flow of parent (fork() != 0, which hits break) versus child (fork() == 0, which hits continue) in each loop iteration.

In each iteration $i \in \{0, 1, 2\}$ :

The calling (parent) process receives a non-zero PID from fork(), skips the if body, executes break;, exits the for loop immediately, and executes printf("Hello!");.
The newly created child process receives 0 from fork(), executes continue;, and advances to the next iteration of the loop.

Thus:

$i = 0$ : Initial process $P_0$ spawns child $P_1$ and breaks out of the loop.
$i = 1$ : $P_1$ spawns child $P_2$ and breaks out of the loop.
$i = 2$ : $P_2$ spawns child $P_3$ and breaks out of the loop; $P_3$ increments $i$ to $3$ and terminates the loop normally.

All $4$ processes ( $P_0, P_1, P_2, P_3$ ) execute printf("Hello!"); once, for a total of 4 times.

Final answer

Common trap

Assuming $2^3 = 8$ processes are created by overlooking the break; statement executed by the parent.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2026 Computer Science and Information Technology - Session 1 (CS1)
Question: 63 of 65
Section: Computer Science and Information Technology

Report an error in this question

GATE questions are the work of the organising institutes. This site is independent and is not affiliated with them.

Question

Solution

Source