unit Unit2;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TFrmLogin = class(TForm)
    LblUserName: TLabel;
    LblPass: TLabel;
    EdtUser: TEdit;
    EdtPass: TEdit;
    BtnEnter: TButton;
    BtnBack: TButton;
    procedure BtnEnterClick(Sender: TObject);
    procedure BtnBackClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  FrmLogin: TFrmLogin;

implementation

{$R *.dfm}
uses
  unit1, unit3;
procedure TFrmLogin.BtnEnterClick(Sender: TObject);
var
  Username, Password, User, Pass, Textstring : string;
  userfile : Textfile;
  done ,done2 : boolean;
begin
  Assignfile (userfile, 'LoginDetails.txt');
  reset(userfile);
  username := EdtUser.text;
  Password := EdtPass.Text;

  done := false;
  while ((done = false) AND (EOF(userfile)= false)) do
    Begin
      Readln(userfile, TextString);
      User := Textstring;
      Readln(userfile, TextString);
      pass := Textstring;
      if ((Username = User) AND (Password = Pass)) then
        begin
          showmessage (' Success');
          Done := True;
          close;
          FrmGraphMenu.show;
        end;

        if (EOF(userFile)AND(done = False)) then
        begin
          Showmessage ('Try Again');
        end;
        //Readln
    End;  //End of while
    CloseFile(UserFile);
 end;