一：function Pos(Substr: string; S: string): Integer;

註解：該函式是查詢元素第一次出現的位置。 

1....  框圖：

2 .....程式碼：

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Button1: TButton;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);

  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
str1,word:string;
i,j:integer;
begin
  str1:='dsf4654f6<ds>ad<<<' ;
  word:=Edit1.Text;
  j:=pos(word,str1);//在字串str1中查詢"<"
  if j<>0 then   //得到的j是字串中出現的位置，是整型
  showmessage('<'+'在第'+inttostr(j)+'個位置');  //第十個位置
end;

end.
 

 3....執行結果：