Delphi Basics : Randomize command

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

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;

Show 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