C语言设计：编写一个带命令行参数的程序,实现整数四则运算。

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
char x;
float a, b;
if (argc != 4)
{
printf("You may use program %s like this: %s 10 + 20\n", argv[0], argv[0]);
return 1;
}
x = argv[2][0];
a = atof(argv[1]);
b = atof(argv[3]);
switch (x)
{
case '+':
printf("%.2f", a + b);

break;
case '-':
printf("%.2f", a - b );
break;
case '/':
if (argv[3] == 0)
{
printf("Error, You put 0 as a divisor\n");
break;
}
else
{
printf("%.2f", a / b);
}
break;        
case '*':
case 'x':
case 'X':
printf("%.2f", a * b);