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.

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 141
  ClientWidth = 251
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Button1: TButton
    Left = 88
    Top = 8
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 0
    OnClick = Button1Click
  end
  object Button2: TButton
    Left = 88
    Top = 39
    Width = 75
    Height = 25
    Caption = 'Button2'
    TabOrder = 1
    OnClick = Button2Click
  end
  object Button3: TButton
    Left = 88
    Top = 70
    Width = 75
    Height = 25
    Caption = 'Button3'
    TabOrder = 2
    OnClick = Button3Click
  end
  object Button4: TButton
    Left = 88
    Top = 101
    Width = 75
    Height = 25
    Caption = 'Button4'
    TabOrder = 3
    OnClick = Button4Click
  end
end