字符由char类型表示，只能容纳256个不同的值。

下面列出了一些有用的字符函数-

• isLower     -  确定是否使用小写字符
• isUpper     -  确定是否大写字符
• isAlpha     -  确定是Unicode字母数字字符(通常是字母还是数字)
• isWhite     -  确定是否有空格字符
• toLower    -  产生给定字符的小写字母
• toUpper    -  产生给定字符的大写字母

import std.stdio;
import std.uni;

void main() { 
   writeln("Is ğ lowercase? ", isLower('ğ')); 
   writeln("Is Ş lowercase? ", isLower('Ş'));  
   
   writeln("Is İ uppercase? ", isUpper('İ')); 
   writeln("Is ç uppercase? ", isUpper('ç')); 
   
   writeln("Is z alphanumeric? ",       isAlpha('z'));  
   writeln("Is new-line whitespace? ",  isWhite('\n')); 
   
   writeln("Is underline whitespace? ", isWhite('_'));  
   
   writeln("The lowercase of Ğ: ", toLower('Ğ')); 
   writeln("The lowercase of İ: ", toLower('İ')); 
   
   writeln("The uppercase of ş: ", toUpper('ş')); 
   writeln("The uppercase of ı: ", toUpper('ı')); 
}

编译并执行上述代码后，将产生以下输出-

Is ğ lowercase? true 
Is Ş lowercase? false 
Is İ uppercase? true 
Is ç uppercase? false
Is z alphanumeric? true 
Is new-line whitespace? true 
Is underline whitespace? false 
The lowercase of Ğ: ğ 
The lowercase of İ: i 
The uppercase of ş: Ş 
The uppercase of ı: I 

读取字符

我们可以使用 readf 读取字符，如下所示。

readf(" %s", &letter);

由于D编程支持unicode，因此为了读取unicode字符，我们需要读取两次并写入两次才能获得预期的输出。该如下所示。

import std.stdio;

void main() { 
   char firstCode; 
   char secondCode; 
   
   write("Please enter a letter: "); 
   readf(" %s", &firstCode); 
   readf(" %s", &secondCode); 
   
   writeln("The letter that has been read: ", firstCode, secondCode); 
} 

编译并执行上述代码后，将产生以下输出-

Please enter a letter: ğ 
The letter that has been read: ğ