System.Random Function

Generates random numbers within a specified range.

Pascal

function Random(const ARange: Integer): Integer; overload;
function Random: Extended; overload;

C++

int Random(const int ARange);
Extended Random();

File

System

Description

In Delphi code, Random returns a random number within the range 0 <= X < Range. If Range is not specified, the result is a real-type random number within the range

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0 <= X < 1.

To initialize the random number generator, add a single call Randomize or assign a value to the RandSeed variable before making any calls to Random.

Note: Because the implementation of the Random function may change between compiler versions, we do not recommend using Random for encryption or other purposes that require reproducible sequences of pseudo-random numbers.

Delphi Examples:

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{
This example draws many rectangles of various sizes and
colors on a form maximized to fill the entire screen. To run
the code, drop a TTimer component on the form and use the
object inspector to create the OnTimer and OnActivate event
handlers.
}
var
  X, Y: Integer;
procedure TForm1.FormActivate(Sender: TObject);
begin
  WindowState := wsMaximized;
  Timer1.Interval := 50;
  Randomize;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  X := Random(Screen.Width - 10);
  Y := Random(Screen.Height - 10);
  Canvas.Pen.Color := Random(65535);
  case Random(5) of
    0: Canvas.Pen.Style := psSolid;
    1: Canvas.Pen.Style := psDash;
    2: Canvas.Pen.Style := psDot;
    3: Canvas.Pen.Style := psDashDot;
    4: Canvas.Pen.Style := psDashDotDot;
  end;
  Canvas.Rectangle(X, Y, X + Random(400), Y + Random(400));
end;