unit1.pas

教学＂求圆的面积和圆的周长＂的程序

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Edit1: TEdit;
    Label2: TLabel;
    Button1: TButton;
    Button2: TButton;
    Label3: TLabel;
    Label4: TLabel;
    Label5: TLabel;
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button2Click(Sender: TObject);
begin
form1.Close;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
r,c,s:real;
const pi=3.14159;
begin

r:=strtofloat(edit1.Text);
if r<>0.0 then
 begin
  c:=2*pi*r;
  s:=pi*sqr(r);
  label2.Caption:=floattostr(c);
  label3.Caption:=floattostr(s);
 end;
end;

end.