Question

How can I use a variable in one .c file when it has been previously defined in another .c file?

Answer 1

In fileA.c:

int myGlobal = 0;

In fileA.h

extern int myGlobal;

In fileB.c:

#include "fileA.h"
myGlobal = 1;

So this is how it works:

• the variable lives in fileA.c
• fileA.h tells the world that it exists, and what its type is (int)
• fileB.c includes fileA.h so that the compiler knows about myGlobal before fileB.c tries to use it.