# include<stdio.h>
float min(float,float);

int main(void)
{
    float num1,num2;
    float MinNum;
    printf("please enter two numbles('q' to quit)\n");
    while(scanf("%f%f",&num1,&num2)==2)
    {
        MinNum=min(num1,num2);
        printf("the  num is :%.2f\n",MinNum);
        printf("Do you want continue?\n");
    }
    return 0;
}

float min(float x,float y)
{
  // float min;
    if(x<y)
        return x;
    else 
        return y;
    
}

程序是这样的，当函数类型及变量类型变为double后，执行不正常，执行结果如下：
the num is :-925596044...(即垃圾值)

改成double后，相应的scanf里面应该改为scanf("%lf%lf",&num1,&num2)，
同时printf改为printf("the  num is :%.2lf\n",MinNum);

谢谢！