Multiple declarations same of variables inside and outside for loop

Question

#include <stdio.h>
int main()
{
    int i;
    for ( i=0; i<5; i++ )
    {
        int i = 10;
        printf ( "%d", i );
        i++;
    }
return 0;
}

In this variable i is declared outside the for loop and it is again declared and initialized inside for loop. How does C allows multiple declarations?

Answer 1

The i outside the loop and the i inside the loop are two different variables.

• The outer i will live for the entire duration of main.

• The inner i will only live for the duration of one loop iteration.

The inner one shadows the outer one in this scope:

{
    int i = 10;
    printf ( "%d", i );
    i++;
}

Due to shadowing rules, it is impossible to refer to the outer one while inside the aforementioned scope.

---

Note that it is impossible to declare two variables with the same name in the same scope:

{
    int i = 0;
    int i = 1; // compile-time error
}