Call by reference

/* call by value */
#include <stdio.h>
 
void increment(int a)
{
  a = a+1;
}
 
int main()
{
  int a;
  a = 10;
  increment(a);
  printf("a = %d",a);
  return 0;
}

/* call by reference */
#include <stdio.h>
 
void increment(int *p)
{
  *p = *p + 1;
}
 
int main()
{
  int a;
  a = 10;
  increment(&a);
  printf("a = %d",a);
  return 0;
}