Creating a dynamic array at runtime in Delphi Pascal

Creating a dynamic array the delphi 3 way
you must declare a constant value of the maximum size you might ever need
which requires some calculation ­ you do not want to declare to small a size
or you will go out of bounds on the array
next you must declare a type of the array you want in the type section
in the var declaration you declare a pointer to this type
Because you have declared a pointer to this type of array, and not the array
itself, no memory is allocated for the array at that time, but rather for the
pointer to the array
in your code you must then use 'GetMem' to actually allocate memory to the
dynamic array of the amount you will need as calculated at runtime
declaring a dynamic array in Delphi 5 is simpler
var somearray : array of char
in the var declaration omit the element count normally found in an array
declaration
then in the code dynamically allocate memory for the array based on calculations
made at runtime using SetLength
SetLength(somearray, thelength * sizeof(elementtype))
Depending on the type of variable in the array you can dispose of it
using Finalize or by setting a new dynamic length of nothing
In regards to using Finalize the Delphi help notes indicate that
" If the variable specified in a call to Finalize contains no long strings
and Variants, the compiler eliminates the call and generates no code for it."
}
unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
 StdCtrls;
type
 TForm1 = class(TForm)
   Button1: TButton;
   Edit1: TEdit;
   Memo1: TMemo;
   Button2: TButton;
   procedure Button1Click(Sender: TObject);
   procedure Button2Click(Sender: TObject);
   procedure FormCreate(Sender: TObject);
 private
   { Private declarations }
 public
   { Public declarations }
 end;
const
 MaxArraySize = 1000 * SizeOf(char);
type
 CharArrayType = array[1..MaxArraySize] of char;
var
 Form1: TForm1;
 ADynamicCharArray :  ^CharArrayType;
 NumChars : integer;
implementation
{$R *.DFM}
{type a string into the edit box
and then retrieve each char and put into a dynamic array of char}
procedure TForm1.Button1Click(Sender: TObject);
var c : char; s : string;  i : integer;
begin
    s := Edit1.Text;
    NumChars := length(s);
    ADynamicCharArray := AllocMem(NumChars * sizeof(char));
    For i := 1 to Numchars do begin
        c := s[i];
        ADynamicCharArray^[i] := c;
    end;
    {Output chars in the array to memo}
    for i := 1 to NumChars do begin
        c := ADynamicCharArray[i];
        Memo1.Lines.Append(c);
    end;
    Button1.Enabled := false;
    Button2.Enabled := true;
end;
{clear the memo, edit box, and free dynamic array}
procedure TForm1.Button2Click(Sender: TObject);
begin
    Edit1.Text := '';
    Memo1.Lines.Clear;
    FreeMem(ADynamicCharArray, NumChars * sizeof(char));
    Button1.Enabled := true;
    Button2.Enabled := false;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
       Button1.Enabled := true;
       {don't allow the Freeing of Memory for non allocated array}
       Button2.Enabled := false;
end;
end.