C Program Compilation Analysis

This question asks to identify which of the three given C programs (P1, P2, P3) will compile successfully without errors. We need to analyze the variable declarations and scope rules in each program.

Program P1 Compilation

Program P1:

$#include <stdio.h>
int a=5; // Global variable 'a'
int main(){
    int a=7; // Local variable 'a'
    return(0);
}
$

• P1 declares a global variable $a$ and a local variable $a$ inside $main$.
• In C, having a local variable with the same name as a global variable is allowed. The local variable $a$ shadows the global variable $a$ within the scope of the $main$ function.
• Therefore, P1 will compile without any errors.

Program P2 Compilation

Program P2:

$#include <stdio.h>
int main(){
    int a=5;
    int a=7; // Error: Redefinition of 'a'
    return(0);
}
$

• P2 attempts to declare an integer variable $a$ twice within the same scope (the $main$ function).
• Redeclaring a variable within the same scope is illegal in C.
• Therefore, P2 will result in a compilation error (redefinition of variable 'a').

Program P3 Compilation

Program P3:

$#include <stdio.h>
int main(){
    int a=5;
    float a=7; // Error: Redefinition of 'a'
    return(0);
}
$

• P3 attempts to declare two variables named $a$ within the same scope (the $main$ function), one of type $int$ and the other of type $float$.
• Even though the types are different, declaring two variables with the same name in the same scope is not allowed.
• Therefore, P3 will result in a compilation error (redefinition of variable 'a').

Conclusion

Based on the analysis:

• P1 compiles successfully.
• P2 fails due to redeclaration of $a$.
• P3 fails due to redeclaration of $a$.

Thus, only P1 will compile without any error.