我想做的是
先打了价钱 , 再询问付几多钱
并显示还要付的余额
直至付完为止

/* Trial for break function*/
#include<stdio.h>
int main()
{
    int price,pay=0,remain;
    printf("What is the price? ");scanf("%d",&price);
    while (price>0)
        {
            printf("How much do you pay? ");scanf("%d",&pay);
            if (pay<=0)
                printf("You need to enter the positive no.\n");
            else
                price=price-pay;
                printf("You still need to pay %d\n",price);
            if(price<=0)
                break;
    }
        printf("You have clear the pay\n");
    return 0;
}

问题是 : 假若还剩 5元 , 我付了8元
他会先显示我还剩 -3 元
才说我已经付清
如何直接说我付清了, 而不显示那负数?
还有一开始输入价钱时
要展开 if 才可以确保输入正数吗?

只在学校上了两课最基本的
想自己先自习一下
却发现真的很有难度...

问题多多的,抱歉了...

#include<stdio.h>
int main()
{
    int price,pay=0,remain;
    printf("What is the price? ");
    scanf("%d",&price);
    while (price>0)
        {
            printf("How much do you pay? ");
            scanf("%d",&pay);
            if (pay<=0)
                printf("You need to enter the positive no.\n");
            else
               {
                price=price-pay;
                if(price>0)
                printf("You still need to pay %d\n",price);
                else
                break;
                }
       }
        printf("You have clear the pay\n");
    return 0;
}

来过

学习...

#include<stdio.h>
main()
{
    int price,pay,remain;
    while(1)
    {
       printf("what is the price:\n");
       scanf("%d",&price);
       if(price>0)
           break;
    }
    while(price>0)
    {
    printf("how much do you pay?\n");
    scanf("%d",&pay);
    if(pay<=0)
        printf("you need to enter the positive now\n");
    else
    {
        if((price=price-pay)>0)
            printf("you still need to pay:%d\n",price);
        else
        {
            remain=(-1)*price;
            break;
        }


    }
    }
    printf("you have cleared the pay\n");
    printf("you can get back:$%d\n",remain);
    return(0);
}