C语言学习：用C语言实现简单的计算器

用C语言编写一个简单的可以进行加减乘除运算混合运算的计算器的方法：

# include

int main() {

char operator;

  double firstNumber,secondNumber;

  printf("输入操作符 (+, -, *,/): ");

  scanf("%c", &operator);

  printf("输入两个数字: ");

  scanf("%lf %lf",&firstNumber, &secondNumber);

  switch(operator)

{

case '+':

          printf("%.1lf + %.1lf = %.1lf",firstNumber, secondNumber, firstNumber + secondNumber);

          break;

      case '-':

          printf("%.1lf - %.1lf = %.1lf",firstNumber, secondNumber, firstNumber - secondNumber);

          break;

      case '*':

          printf("%.1lf * %.1lf = %.1lf",firstNumber, secondNumber, firstNumber * secondNumber);

          break;

      case '/':

          printf("%.1lf / %.1lf = %.1lf",firstNumber, secondNumber, firstNumber / secondNumber);

          break;

      // operator doesn't match any case constant (+, -, *, /)

default:

          printf("Error! operator is not correct");

  }

return 0;

}