what is call by value and call by reference code example

Example 1: , Call by Reference,

/* function definition to swap the values */
void swap(int *x, int *y) {

   int temp;
   temp = *x;    /* save the value at address x */
   *x = *y;      /* put y into x */
   *y = temp;    /* put temp into y */
  
   return;
}

Example 2: call by reference

//Call By Reference

#include<stdio.h>
void function(int *, int *);       //function declaration
int main()
{
	int a,b;
    
    printf("Enter first number: ");
    scanf("%d",&a);
    printf("Enter second number: ");
    scanf("%d",&b);
    
    function(&a,&b);    //passing the address of both the variables( CALL BY REFERENCE)

}
void function(int *p,int *q)     //function defination
{
   printf("printing variables from function a=%d b=%d",*p,*q);
}
//code by Dungriyal..

Example 3: what is call by value and call by reference

/* function definition to swap the values */
void swap(int *x, int *y) {

   int temp;
   temp = *x;    /* save the value at address x */
   *x = *y;      /* put y into x */
   *y = temp;    /* put temp into y */
  
   return;
}