try yourself |run program

#include <stdio.h>
#include <conio.h>

 int n = 100; /* global */
void f1(){
 printf("\n value of n = %d",n);
}

void f2(int a){
 printf("\n value of a = %d",a);
}

void main(){
 clrscr();
 f1();
 f2(n);
 getch();
}

Program Output

value of n = 100
value of a = 100