Program for Call By Value in C

#include<stdio.h>
#include<conio.h>
int main()
{
 int n1,n2,x;
 int call_by_value();
 n1=6;
 n2=9;
 printf("n1 = %d and n2 = %d\n",n1,n2);
 x=call_by_value(n1,n2);
 printf("x = %d",x);
}

call_by_value(p1,p2)
int p1,p2;
{
 int sum;
 sum = p1 + p2;
 p1 = p1 + 2;
 p2 = p2 + p1;
 printf("p1 = %d and p2 = %d\n",p1,p2);
 return(sum);
}