DelphiBasics
Randomize
Procedure
Reposition the Random number generator next value System unit
 procedure Randomize ;
Description
The Randomize procedure is used in conjunction with the Random function. It repositions the random number generator in its sequence of 232 pseudo random numbers.
 
Randomize uses the time of day as the seed for this repositioning, so should provide a reliable method of creating an unpredictable sequence of numbers, even if they are a part of a predetermined sequence.
Related commands
Random Generate a random floating point or integer number
RandomRange Generate a random integer number within a supplied range
RandSeed Reposition the Random number generator next value
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Example code : Run this code twice to see the effect of Randomize
// Full Unit code.
// -----------------------------------------------------------
// You must store this code in a unit called Unit1 with a form
// called Form1 that has an OnCreate event called FormCreate.
 
unit Unit1;
 
interface
 
uses
  // The System unit does not need to be defined
  SysUtils,
  Forms, Dialogs;
 
type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  end;
 
var
  
Form1: TForm1;
 
implementation
{$R *.dfm} // Include form definitions
 
procedure TForm1.FormCreate(Sender: TObject);

var
  int   : Integer;
  i     : Integer;

begin
  // If you run this program twice, only the first 5 values
  // will be guaranteed to be the same each time - randomize
  // repositions into a different part of the pseudo sequence
  // of random numbers.

  // Get an integer random number in the range 1..100
  ShowMessage('Fixed first 5 random numbers');
  for i := 1 to 5 do
  begin
    int := 1 + Random(100);    // The 100 value gives a range 0..99
    ShowMessage('int = '+IntToStr(int));
  end;

  // Now randomize to reposition
  Randomize;
  ShowMessage('');

  // Get an integer random number in the range 1..100
  ShowMessage('Random next 5 numbers');
  for i := 1 to 5 do
  begin
    int := 1 + Random(100);    // The 100 value gives a range 0..99
    ShowMessage('int = '+IntToStr(int));
  end;
end;
 
end.
Hide full unit code
   Fixed first 5 random numbers
   int = 1
   int = 4
   int = 87
   int = 21
   int = 28
  
   Random next 5 numbers
   int = 35
   int = 74
   int = 45
   int = 50
   int = 31
 
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