/* Lecture #5 Demo
 *
 * Swap
 *
 * A function uses pointers to swap the contents of two integers.
 */
#include <stdio.h>

/* swap() swaps the values of two integer locations.  
 * Note that swap's parameters are two integer *pointers*, so it must be
 *  passed the *address* of locations in memory containing the integers. 
 */
void swap (int *px, int *py)
{
	int temp = *px;		/* Temp gets *contents* pointed to by px. */
	*px = *py;		/* Location pointed to by px gets value   */
				/*  pointed to by py -- note that the     */
				/*  addresses in px and py are not        */
				/*  changing here.                        */
	*py = temp;		/* Move the val originally pointed to by  */
				/*  px into location pointed to by py.    */
}

int main()
{
	int x = 50, y = 100;

	printf("x = %d, y = %d\n", x, y);

	swap(&x, &y);		/* swap requires pointers to x and y,     */
				/*  so we must pass not the values of x   */
				/*  and y, but rather the *addresses* of  */
				/*  x and y.                              */

	printf("x = %d, y = %d\n", x, y);

	return 0;
}