GATE CS 2025 Set 1 Q.34: Pointers, Arrays and Strings

#include <stdio.h>
void foo(int *p, int x){
    *p=x;
}
int main(){
    int *z;
    int a = 20, b = 25;
    z = &a;
    foo(z,b);
    printf("%d",a);
    return 0;
}

The output of the given C program is __________. (Answer in integer)

Your answer

Official answer and solution

Official answer: 25
From: Official GATE 2025 answer key

Solution

Trace how passing pointer z = &a to foo modifies a via dereferencing *p = x.

In main(), a is initialized to 20, b to 25, and pointer z is assigned the address of a (z = &a).
Calling foo(z, b) passes p = &a and x = 25.
Inside foo, *p = x; writes 25 directly to the memory location of a.
printf("%d", a); prints 25.

Final answer

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

Source

Paper: GATE 2025 Computer Science and Information Technology - Session 1 (CS1)
Question: 34 of 65
Section: Computer Science and Information Technology

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