Delphi Basics : RandSeed command

DelphiBasics

RandSeed
Variable

Reposition the Random number generator next value

System unit

var RandSeed : LongInt;

Description

The RandSeed variable is used in conjunction with the Random function. It changes the seed used that Delphi uses to generate its range of 2³² pseudo random numbers.

Related commands

Random		Generate a random floating point or integer number
Randomize		Reposition the Random number generator next value
RandomRange		Generate a random integer number within a supplied range

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Example code : Run this code twice to see the effect of RandSeed

var
  int   : Integer;
  i     : Integer;
  hours, mins, secs, milliSecs : Word;

begin
  // Get random numbers using the default random seed value
  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 change the random seed to the milliseconds value
  // of the current time
  DecodeTime(now, hours, mins, secs, milliSecs);
  ShowMessage('');
  ShowMessage('Setting randSeed to value : '+IntToStr(milliSecs));
  ShowMessage('');
  RandSeed := milliSecs;

  // 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

  Setting random seed to value : 660

  Random next 5 numbers
  int = 72
  int = 62
  int = 28
  int = 63
  int = 44