GATE CS 2026 Set 2 Q.19: Functions, Recursion, Scope and Storage Classes

Consider the following three ANSI-C programs, P1, P2, and P3.

/* P1 */
#include <stdio.h>
int a=5;
int main(){
    int a=7;
    return(0);
}

/* P2 */
#include <stdio.h>
int main(){
    int a=5;
    int a=7;
    return(0);
}

/* P3 */
#include <stdio.h>
int main(){
    int a=5;
    float a=7;
    return(0);
}

Which one of the following statements is true?

Only P1 will compile without any error

Only P2 will compile without any error

Only P3 will compile without any error

All three programs P1, P2, and P3 will compile without any error

Official answer and solution

Official answer: A
From: Official GATE 2026 answer key

Solution

Check C scoping rules for global vs. local shadowing (P1) and duplicate identifier declarations in the same block scope (P2, P3).

In P1, the first int a=5; is in file (global) scope, while int a=7; inside main() is in block (local) scope. Local variable a legally shadows the global a, so P1 compiles without error.
In P2 and P3, a is declared twice within the exact same block scope (main), causing a redefinition/conflicting-types compilation error.

Hence only P1 compiles without any error.

Final answer

Option (A)

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 2 (CS2)
Question: 19 of 65
Section: Computer Science and Information Technology

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