请问这个程序哪里错了啊   

#include<stdio.h>
int main()
{
    float a,b;
    char coperator;
    printf("please type in your expression(a+b)\n");
    scanf("%f %c %f",&a,&coperator,&b);
    switch(coperator){
        case'+':printf("%.2f\n",a+b);break;
        case'-':printf("%.2f\n",a-b);break;
        case'*':printf("%.2f\n",a*b);break;
        case'/':if(b==0) printf("division by zero error found\n");
                else printf("=%.2f\n",a/b);break;
        case'%':printf("%%",a%b);break;
        default:printf("错误\n");break;}
            return 0;

}