scanf_s

 1 #include<stdio.h>
 2 
 3 int main()
 4 {
 5     double value1, value2;
 6     char op;
 7 
 8     printf("Type in an expression:");
 9     scanf_s("%lf%c%lf", &value1, &op,sizeof(op), &value2);    //scanf_s在输入字符时，在地址的后面要加上sizeof
10     
11     if (op == ‘+‘)
12     {
13         printf("%.2f\n", value1 + value2);
14     }
15     else
16     {
17         if (op == ‘-‘)
18         {
19             printf("%.2f\n", value1 - value2);
20         }
21         else
22         {
23             if (op == ‘*‘)
24             {
25                 printf("%.2f\n", value1 * value2);
26             }
27             else
28             {
29                 if (op == ‘/‘)
30                 {
31                     printf("%.2f\n", value1 / value2);
32                 }
33                 else
34                 {
35                     printf("Unknow operator!\n");
36                 }
37             }
38         }
39     }
40         
41     return 0;
42 }