An example to how pointers in C work.

C - Pointers.c

int main()
{
	int i, j;
	int *p;
	p = &i;
	*p = 5;
	j = i;
	printf("addresses: i = %d, j = %d, p = %d\n", &i, &j, p);
	printf("values: i = %d, j = %d, p = %d\n", i, j, *p);
}

C - PointersInFunctions.c

#include <stdio.h>

void swap1(int *i, int *j)
{
	int t;
	t = *i;
	*i = *j;
	*j = t; 
}

void swap2(int *i, int *j)
{
	int *t;
	t = i;
	i = j;
	j = t;
}

void main()
{
	int a, b;
	a = 5;
	b = 10;
	printf("%d %d\n", a, b);
	swap1(&a, &b);
	printf("%d %d\n", a, b);
	swap2(&a, &b);
	printf("%d %d\n", a, b);
}