procedure TForm1.Button1Click(Sender: TObject);
var i: integer;
begin
Button1.Caption:= 'Pause';
for i:=1 to N do ListBox1.Items.Add( FloatToStr(i) );
Button1.Caption:= 'RUN';
end;

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    Button1: TButton;
    Label1: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    CurState:longint;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}


procedure TForm1.FormCreate(Sender: TObject);
begin
     CurState:=0;
end;

procedure TForm1.Button1Click(Sender: TObject);
var i:longint;
begin
     if CurState=2 then
     begin
          CurState:=1; //set to Run
          Button1.Caption:='Pause';
          exit;
     end else
     if CurState=1 then
     begin
          CurState:=2; //set to Pause
          Button1.Caption:='Resume';
          exit;// if we already run it
     end else
     if CurState=0 then
     begin
          CurState:=1;//Run state
          Button1.Caption:='Pause';
     end;

     for i:=0 to 1000000 do
     begin
          ListBox1.Items.Add(inttostr(i));
          Application.ProcessMessages;
          Label1.Caption:=inttostr(i);
          while CurState=2 do Application.ProcessMessages; //in pause mode
     end;
     CurState:=0;
     Button1.Caption:='Run';
end;

end.

var
  p : PAnsiChar;
begin
  StrPCopy(p,'');
end;

var
  p : array [0..255] of char;
begin
  StrPCopy(p,'');//Нафига? пустая строка?
  StrPCopy(p,'Нафига она полная ?');
end;