我是新手，在做一道练习题，做个小计算器程序。要求用到goto实现循环。下面是我的程序：#include<stdio.h>

int main(void)
{
    double Number1 = 0.0;
    double Number2 = 0.0;
    char Operation = 0;
    char Answer = 0;
start:
    printf("\n请输入运算式：\n\t");
    scanf("%lf %c %lf",&Number1,&Operation,&Number2);
    /*********检测数据的可靠性并输出计算结果********/
     switch(Operation)
     {
             case '+':
                 printf("\t= %lf\n",Number1 + Number2);
                 break;
                 
             case '-':
                 printf("\t= %lf\n",Number1 - Number2);
                 break;
                 
             case '*':
                 printf("\t= %lf\n",Number1 * Number2);
                 break;
                 
             case '/':
                 if (Number2 == 0)
                 printf("\a\nERROR!除数不能为0！！\n");
                 else
                 printf("\t= %lf\n",Number1 / Number2);
                 break;
                 
             case '%':
                 if ((long)Number2 == 0)
                 printf("\a\nERROR!除数不能为0！！\n");
                 else
                 printf("\t= %ld\n",(long)Number1 % (long)Number2);
                 break;
                 
             default :
                 printf("\a\nERROR!错误的运算符号\n");
                 break;
     }
choose:
       printf("\n继续计算？Y/N\n");
       scanf(" %c",&Answer);                       /**********求解释********就是这行里的%前的那个空格*******去掉就不能循环了*****/
       switch(Answer)
       {
                     case 'Y':case 'y':
                          goto start;
                          break;
                          
                     case 'N':case 'n':
                          printf("\n谢谢使用，再见！\n");
                          break;
                          
                     default:
                             printf("\n输入错误，请重新选择。（Y/N）\n");
                             goto choose;
                             break;
       }
   
 return 0;   
}

scanf(" %c",&Answer);空格的意义是跳过输入的空字符（空格，换行。。）至第一个非空字符。当用键盘输入的时候，会按ENTER产生换行符，可能是为了滤除这些空字符吧。

啊哈哈，就是的！因为前面输入运算式子的时候结尾用的是回车。呵呵，多谢你了！

共同进步吧。scanf(" %c",&Answer); ，scanf("%c ",&Answer);以及scanf("%1c",&Answer);之类的知道就好办了。不然，有时代码的功能实现就会和预料的有些差异，让人纠结。