#include <stdio.h> int main() { double a = 0.0; double b = 0.0; char c = 0; scanf("%lf%c%lf", &a, &c, &b);//输入 if ('+' == c)//判断加法 { printf("%.4lf+%.4lf=%.4lf\n", a, b, a + b); } else if ('-' == c)//判断减法 { printf("%.4lf-%.4lf=%.4lf\n", a, b, a - b); } else if ('*' == c)//判断乘法 { printf("%.4lf*%.4lf=%.4lf\n", a, b, a * b); } else if ('/' == c)//判断除法 { if (0.0 == b)//判断操作数2是否为零 { printf("Wrong!Division by zero!"); } else { printf("%.4lf/%.4lf=%.4lf\n", a, b, a / b); } } else//判断运算符号是否非法 { printf("Invalid operation!"); } return 0; }