/*
   pointers.c

   Written in CS 332 by Jeff Ondich and friends
   on March 31, 2010.

   Some simple pointer manipulations in C.
 */

#include <stdio.h>

void badswap(int j, int k);
void goodswap(int *p, int *q);

int main()
{
    // Simple use of & and *.
    int k = 5;
    int *ptr;
    ptr = &k;
    *ptr = 6;
    printf("Here's your number: %d\n", k);

    // Try swapping two variables.
    int a = 10;
    int b = 20;
    printf("Before badswap: a = %d, b = %d, &a = 0x%08x\n", a, b, (unsigned int)(&a));
    badswap(a, b);
    printf("After badswap: a = %d, b = %d\n", a, b);

    printf("Before goodswap: a = %d, b = %d, &a = 0x%08x\n", a, b, (unsigned int)(&a));
    goodswap(&a, &b);
    printf("After goodswap: a = %d, b = %d\n", a, b);

    return 0;
}

void badswap(int j, int k)
{
    printf("Start of badswap: j = %d, k = %d, &j = 0x%08x\n", j, k, (unsigned int)(&j));
    int tmp = j;
    j = k;
    k = tmp;
    printf("End of badswap: j = %d, k = %d\n", j, k);
}

void goodswap(int *p, int *q)
{
    int tmp = *p;
    *p = *q;
    *q = tmp;
}