isalnum ( )【C语言库函数源代码】

【C语言库函数源代码】

【本程序在Dev C++ 4.9.9.2 下编译通过】

int my_isalnum ( int ch )

{

   return (unsigned int)((ch | 0x20) - 'a') < 26u  ||

         (unsigned int)( ch - '0') < 10u;

}//测试参数ch是否是字母(A-Z,大小写均可)或数字（0-9）

int main()

{

   char ch = 'c';

 

   if(my_isalnum(ch))

      printf("%c is English Character or Number!\n",ch);

   else

      printf("%c is not a English Character and Number!\n",ch);

 

   ch = '1';

 

   if(my_isalnum(ch))

      printf("%c is English Character or Number!\n",ch);

   else

      printf("%c is not a English Character and Number!\n",ch);

 

   ch = '!';

 

   if(my_isalnum(ch))

      printf("%c is English Character or Number!\n",ch);

   else

      printf("%c is not a English Character and Number!\n",ch);

 

   system("pause");

   return 0;

}