代码文件:
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unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
Button3: TButton;
Button4: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

uses Character;

{Character.ToUpper}
procedure TForm1.Button1Click(Sender: TObject);
var
c: Char;
str: string;
begin
c := ToUpper('a');
str := ToUpper('Delphi');
ShowMessageFmt('%s, %s', [c, str]); {A, DELPHI}
end;

{Character.ToLower}
procedure TForm1.Button2Click(Sender: TObject);
var
c: Char;
str: string;
begin
c := ToLower('A');
str := ToLower('Delphi');
ShowMessageFmt('%s, %s', [c, str]); {a, delphi}
end;

{相应的 API 函数: Windows.CharUpper、Windows.CharLower}
procedure TForm1.Button3Click(Sender: TObject);
var
c1,c2: Char;
begin
c1 := Char(CharUpper(PChar('a')));
c2 := Char(CharLower(PChar('B')));
ShowMessageFmt('%s, %s', [c1, c2]); {A, b}
end;

{以前 SysUtils 下有: UpperCase、LowerCase}
procedure TForm1.Button4Click(Sender: TObject);
var
s1,s2: string;
begin
s1 := UpperCase('Delphi');
s2 := LowerCase('Delphi');
ShowMessageFmt('%s, %s', [s1, s2]); {DELPHI, delphi}
end;

end.