其实９楼的代码我运行了一下有错误，一看是r没有定义，所以就改了一下就贴上去了～～勿怪，请原谅～～

谢谢１０楼的提醒，那　return 0;的确是多余的（写多了就．．．呵呵．．）在此表示感谢，我也新手，望多指教，共同进步！！

#include <stdio.h>

int main()
{
    int m, n, temp;
    printf("please input two positive number.\n");
    scanf("%d %d", &m, &n);
    if (m <= 0 || n <= 0)
    {printf("error!");
    return 0;
    }
while (n != 0)
{
    temp = m%n;
    m = n;
    n = temp;
}
printf("the result is:%d\n", m);
return 1;
}

11楼犯了两个小错误，指出来不要生气哦！
1、你加上的r其实已经在局部定义了，你加上其实是画蛇添足
2、return 0;并非多余，是告诉操作系统程序运行成功返回

#include <stdio.h>
#include <stdlib.h>
int main(void)
{
    int m,n,r;
    int m_cup,n_cup;
    scanf("%d %d", &m, &n);
    if(m>0&&n>0)
    {
            m_cup=m;
            n_cup=n;
        while((r=m_cup%n_cup)!=0)
        {
            m_cup=n_cup;
            n_cup=r;
        }
        printf("Greatest common divisor: %d\n", n_cup);
        printf("Lease common multiple  : %d\n", m * n / n_cup);
    }
    else printf("Error!\n");
    system("pause");
    return 0;
}

改进代码
#include <stdio.h>
#include <stdlib.h>
int main()
{
    int m, n;
    printf("Enter two integer:\n");
    scanf("%d %d", &m, &n);


    if (m > 0 && n >0)
    {
        int res;

        while((res = m % n) != 0)
        {
            m = n;
            n = res;
        }

        printf("Greatest common divisor: %d\n", n);
    }
    else printf("Error!\n");
    system("pause");
    return 0;
}