procedure TForm1.EuroButtonClick(Sender: TObject);
var
  Euro, Fr: real;
  S1, S2: string;
begin
  CurrLabel.Caption := 'Euro';
  Euro := StrToFloat(InputEdit.Text);
  Fr := Euro * 40.3399;
  S1 := FormatFloat('0.00', Euro);
  S2 := FormatFloat('0.00', Fr);
  EuroLabel.Caption := S1;
  BEFLabel.Caption := S2;
end;

procedure TForm1.BEFButtonClick(Sender: TObject);
var
  Euro, Fr: real;
  S1, S2: string;
begin
  CurrLabel.Caption := 'BEF';
  Fr := StrToFloat(InputEdit.Text);
  Euro := Fr / 40.3399;
  S1 := FormatFloat('0.00', Euro);
  S2 := FormatFloat('0.00', Fr);
  EuroLabel.Caption := S1;
  BEFLabel.Caption := S2;
end;

// Any text between a double-slash and the end of the line is comments

// Look at this:
S1 := Edit1.Text // the text of Edit1 is assigned to S1

{ Text between a left brace and a right brace is a comment.}

{ Comments between braces can extend over several lines.
  This comments block ends at the end of this line.      }

(* The combination of rounded brackets and asterix may be used
   instead of the brackets { }. This is useful if you want to 
   'nest' comments, which is impossible if you use only ONE 
   type of comments delimiters.
   I never use this notation for comments. I use it to disable
   code temporarily during tests, as in the following example: *)

(*
  { This code seems to be faulty. Let's disable it and see if
    things get better that way.                               }

  Label1.Text := Edit1.Text;
*)

unit euroform;

interface

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

type
  TForm1 = class(TForm)
    InputEdit: TEdit;
    CurrLabel: TLabel;
    Label2: TLabel;
    EuroLabel: TLabel;
    BEFLabel: TLabel;
    Label5: TLabel;
    Label6: TLabel;
    EuroButton: TButton;
    BEFButton: TButton;
    procedure EuroButtonClick(Sender: TObject);
    procedure BEFButtonClick(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

{ Event handler for the OnClick event of EuroButton:
  conversion from Euro to BEF.
  Shows the name of the starting currency, converts the text
  of the Edit-box to Belgian francs, shows the results.      }
procedure TForm1.EuroButtonClick(Sender: TObject);
var
  Euro, Fr: real;
  S1, S2: string;
begin
  // Show the name of the starting currency
  CurrLabel.Caption := 'Euro';

  // Convert the text of the EDIT to a numerical value
  Euro := StrToFloat(InputEdit.Text);

  // Convert from Euro to BEF
  Fr := Euro * 40.3399;

  { Convert the floating point numbers to string-format.
    '0.00' is the 'Format String', meaning:
    'format the result with 2 decimal digits to the right
     of the decimal separator'                            }
  S1 := FormatFloat('0.00', Euro);
  S2 := FormatFloat('0.00', Fr);

  // Put the strings in the CAPTION of the LABELs
  EuroLabel.Caption := S1;
  BEFLabel.Caption := S2;
end;

{ Event handler for the Onclick event of BEFButton:
  conversion from BEF to Euro.
  Shows the name of the starting currency, converts the text
  of the Edit-box to Euro, shows the results.                }
procedure TForm1.BEFButtonClick(Sender: TObject);
var
  Euro, Fr: real;
  S1, S2: string;
begin
  // Show the name of the starting currency
  MuntLabel.Caption := 'BEF';

  // Convert the text of the EDIT to a numerical value
  Fr := StrToFloat(InputEdit.Text);

  // Convert from BEF to Euro
  Euro := Fr / 40.3399;

  { Convert the floating point numbers to string-format.
    '0.00' is the 'Format String', meaning:
    'format the result with 2 decimal digits to the right
     of the decimal separator'                            }
  S1 := FormatFloat('0.00', Euro);
  S2 := FormatFloat('0.00', Fr);

  // Put the strings in the CAPTION of the LABELs
  EuroLabel.Caption := S1;
  BEFLabel.Caption := S2;
end;

end.