How do I share a global variable between c files?

Question

If I define a global variable in a .c file, how can I use the same variable in another .c file?

file1.c:

#include<stdio.h>

int i=10;

int main()
{
    printf("%d",i);
    return 0;
}

file2.c:

#include<stdio.h>

int main()
{
    //some data regarding i
    printf("%d",i);
    return 0;
}

How can the second file file2.c use the value of i from the first file file1.c?

Answer 1

file 1:

int x = 50;

file 2:

extern int x;

printf("%d", x);

Answer 2

Use the extern keyword to declare the variable in the other .c file. E.g.:

extern int counter;

means that the actual storage is located in another file. It can be used for both variables and function prototypes.

Answer 3

using extern <variable type> <variable name> in a header or another C file.