简单练习（四则运算）：

 1 #include "stdafx.h"
 2 #include <iostream>
 3 using namespace std;
 4 
 5 int main()
 6 {
 7     double number1, number2;
 8     double result;
 9     int way;
10 
11     cout << "加法运算请选择  1" << endl;
12     cout << "减法运算请选择  2" << endl;
13     cout << "乘法运算请选择  3" << endl;
14     cout << "除法运算请选择  4" << endl;
15     cout << "请输入运算方法序号:";
16     cin >> way;
17 
18     if (way < 1 || way>4)
19     {
20         cout << "请重新输入序号：";
21         cin >> way;
22     }
23     else
24     {
25         cout << "请输入两个数:";
26         cin >> number1 >> number2;
27     }
28     
29     switch (way)
30     {
31         case 1:cout << "这是加法运算:";
32         {
33             result = number1 + number2;
34         }
35         cout << "和是:" << result << endl;
36         break;
37 
38         case 2:cout << "这是减法运算:";
39         {
40             result = number1 - number2;
41         }
42         cout << "差是:" << result << endl;
43         break;
44 
45         case 3:cout << "这是乘法运算:"; 
46         {
47             result = number1 * number2;
48         }
49         cout << "积是:" << result << endl;
50         break;
51 
52         case 4:cout << "这是除法运算:";
53         {
54             result = number1/number2;
55         }
56         cout << "商是:" << result << endl;
57         break;
58 
59         default:
60             cout << "error!";
61         break;
62     }
63     return 0;
64 }