字符串大小写字母互换

 1 #include <stdio.h>
 2 
 3 int main()
 4 {
 5     char ch;
 6     printf("input characters:");
 7     ch = getchar();
 8     while (ch!='\n')
 9     {
10         if (ch >= 'A' && ch <= 'Z')
11         {
12             ch = ch + ('a' - 'A');        //ascii编码位置
13         }
14         else
15         {
16             if (ch >= 'a' && ch <= 'z')
17             {
18                 ch = ch - ('a' - 'A');
19             }
20         }
21         putchar(ch);
22         ch = getchar();
23     }
24 
25     return 0;
26 }