#include<stdio.h>  
void change(int *num) {    
    printf("Before adding value inside function num=%d \n",*num);    
    (*num) += 100;    
    printf("After adding value inside function num=%d \n", *num);    
}      
int main() {    
    int x=100;    
    printf("Before function call x=%d \n", x);    
    change(&x);//passing reference in function    
    printf("After function call x=%d \n", x);    
return 0;  
}

مثال دیگر :

#include <stdio.h>  
void swap(int *, int *); //prototype of the function   
int main()  
{  
    int a = 10;  
    int b = 20;   
    printf("Before swapping the values in main a = %d, b = %d\n",a,b); // printing the value of a and b in main  
    swap(&a,&b);  
    printf("After swapping values in main a = %d, b = %d\n",a,b); // The values of actual parameters do change in call by reference, a = 10, b = 20  
}  
void swap (int *a, int *b)  
{  
    int temp;   
    temp = *a;  
    *a=*b;  
    *b=temp;  
    printf("After swapping values in function a = %d, b = %d\n",*a,*b); // Formal parameters, a = 20, b = 10   
}