1.交换两个变量的值

#include <stdio.h>
void swap(int *pa, int *pb);

int main(void)
{
    int a = 5, b = 6;
    swap(&a, &b);
    printf("a=%d, b=%d\n", a, b);
    return 0;
}

void swap(int *pa, int *pb)
{
    int t = *pa;
    *pa = *pb;
    *pb = t;
}

2.函数返回多个值，某些值只能通过指针返回

#include <stdio.h>
void minmax(int a[], int len, int *max, int *min);
int main()
{
    int a[] = {1, 2, 3, 4, 5, 6};
    int min,max;

    minmax(a, sizeof(a)/sizeof(a[0]), &max, &min);    
    printf("max=%d, min=%d\n", max, min);

    return 0;
}

void minmax(int a[], int len, int *max, int *min)
{
    int i;
    *min = *max = a[0];
    for ( i=1; i<len; i++) {
        if ( a[i] < *min) {
            *min = a[i];
        }
        if ( a[i] > *max) {
            *max = a[i];
        }
    }
}

3.函数返回运算的状态，结果通过指针返回

#include <stdio.h>
int divide(int a, int b, int *result);

int main(void)
{
    int a = 5;
    int b = 2;
    int c;
    if (divide(a, b, &c)) {
        printf("%d/%d=%d\n", a, b, c);
    }
    return 0;
}

int divide(int a, int b, int *result)
{
    int ret = 1;
    if ( b == 0 ) {
        ret = 0;
    } else {
        *result = a / b;
    }
    return ret;
}