# include <stdio.h>

int fun(int n, int m)
{
    int t,i, x, y;
   
    if(n < m)
    {
        t = n;
        n = m;
        m = t;
    }
        t = n*m;

        if(n % m == 0)
        {
            return n;
        }
        else
        {
            for(; m!=0;)
            {
                i = n%m;
                n = m;
                m = i;
            }
            x = n;
            y = t/x;
            return y;
        }
}

int main(void)
{
    int i, j, k;
    char ch;

    do
    {
        for(k=1; k>0;)
        {
            printf("请输入两个正整数:");
            scanf("%d %d", &i, &j);
            
            if(i<0 || j<0)
            {
                printf("输入数据不合规定，请重新输入!\n");
            }
            else
                --k;
        }

        printf("%d和%d的最小公倍数是%d\n", i, j, fun(i, j));
        printf("按y键继续下一组输,任意键退出\n");
        scanf(" %c", ch);
    }
    while(ch=='y' || ch=='Y');

    printf("已成功退出\n");
    return 0;
}

如图所示

#include <stdio.h>

int fun(int n, int m)
{
    int t,i, x, y;
    
    if(n < m)
    {
        t = n;
        n = m;
        m = t;
    }
        t = n*m;

        if(n % m == 0)
        {
            return n;
        }
        else
        {
            for(; m!=0;)
            {
                i = n%m;
                n = m;
                m = i;
            }
            x = n;
            y = t/x;
            return y;
        }
}

int main(void)
{
    int i, j, k;
    char ch;

    do
    {
        for(k=1; k>0;)
        {
            printf("请输入两个正整数:");
            scanf("%d %d", &i, &j);
            
            if(i<0 || j<0)
            {
                printf("输入数据不合规定，请重新输入!\n");
            }
            else
                --k;
        }

        printf("%d和%d的最小公倍数是%d\n", i, j, fun(i, j));
        printf("按y键继续下一组输,任意键退出\n");
        scanf(" %c", &ch);//少了一个&
    }while(ch=='y' || ch=='Y');

    printf("已成功退出\n");
    return 0;
}

因为这样，所以运行的时候程序就挂了吗？