【C语】字母大写转化为小写小写转为大写

#define _CRT_SECURE_NO_WARNINGS
#include
#include
#define big(ch) (ch >= 'a'&&ch <= 'z')
int  small(char ch)
{
 return ch >= 'A'&&ch <= 'Z';  
}
int main()
{
 char ch;
 while (1)
 {
  ch = getchar();
  if (big(ch))
  {
   putchar(ch - 32);
  }
  else if (small(ch))
  {
   putchar(ch + 32);
  }
 }
 system("pause");
 return 0; 
}