For语句应用判断是否为素数

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);           //“判断”按钮
var
  s,n,i,j: integer;
  m,q: real;
  a: string;
begin
  if edit1.Text = '' then showmessage('不能为空')         //错误判断
  else
  begin
    m := strtofloat(edit1.Text);
    n := round(m);
    if n < 3 then showmessage('请输入一个大于2的整数！');
    s := 0;
    q := sqrt(m);                                         //开方
    j := trunc(q);                                        //取整
    for i := 2 to j do
    begin
      if n mod i = 0 then                                 //取余判断
        s:= 1;
      if s = 0 then                                       //判断是否为素数
        a := '是一个素数'
      else
        a := '不是素数';
      edit2.Text := edit1.Text + a;
    end;
  end;
  edit1.SelectAll;                                        //编辑框1全选
  edit1.SetFocus;                                         //光标设定在编辑框1
end;

procedure TForm1.Button2Click(Sender: TObject);           //“清除”按钮
begin
  edit1.Text := '';
  edit2.Text := '';
end;

end.