程序代码：

#include <math.h>
#include <stdio.h>
#include <conio.h>
int main()
{
    float num1,num2,result;
    char answer,fuhao;
    int right;
    clrscr();/*清平*/
    printf("*********welcome to lin er ming's system*********");
    printf("\n");
     do
     {
         printf("please enter num1,fuhao,num2:");
         scanf("%f%c%f",&num1,&fuhao,&num2);/*可以修改输入，会更好*/
         getchar();
         printf("please enter your answer:");
         scanf("%f",&result);
         getchar();
         switch(fuhao)
         {
             case '+':if(result==(num1+num2)) right=1;
                         else
                           right=0;
                       break;
            case '-':if(result==(num1-num2)) right=1;
                       else
                           right=0;
                       break;
            case '*':if(result==(num1*num2)) right=1;
                else
                    right=0;
                break;
            case '/':if(num2==0) printf("\ninput wrong! ben ben,ha ha!!");
                else
                {
                    if(result==(num1/num2)) right=1;
                    else
                        right=0;
                }
                break;
         }
         if(right)
             printf("\nyou are ringht!");
         else
             printf("\nplease try again!");
         printf("\ndo you want togo on?(please choose 'y'or'n')");
         scanf("%c",&answer);
        
     }while((answer=='y')||(answer=='Y'));
/*这个时候输入y或者Y都不循环，怎么搞的*/
     return 0;
}