Delphi Basics : Random command

DelphiBasics

Random
Function

Generate a random floating point or integer number

System unit

1	function Random():Extended;
2	function Random (LimitPlusOne Integer:Integer;

Description

The Random function generates random numbers. They can be floating point numbers in the range :

0 <= Number < 1.0

or integer numbers in the range :

0 <= Number < LimitPlusOne

Delphi uses a pseudo random number generator that always returns the same sequence of values (2³²) each time the program runs.

To avoid this predictability, use the Randomize procedure. It repositions into this random number sequence using the time of day as a pseudo random seed.

Related commands

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

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Example code : Generate sets of floating point and integer numbers

var
  float : single;
  int   : Integer;
  i     : Integer;

begin
  // Get floating point random numbers in the range 0 <= Number < 1.0
  for i := 1 to 5 do
  begin
    float := Random;
    ShowMessage('float = '+FloatToStr(float));
  end;

  ShowMessage('');

  // Get an integer random number in the range 1..100
  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

  float = 2.3283064365387E-10
  float = 0.031379981256104
  float = 0.861048460006714
  float = 0.202580958604813
  float = 0.2729212641716


  int = 68
  int = 32
  int = 17
  int = 38
  int = 43