By using the FillChar procedure. Here is an example:

procedure TForm .Button Click(Sender: TObject);
type
  TIntRec = record
    i : integer;
    i2: integer;
    i3: integer;
    i4: integer;
    i5: integer;
  end;
var
  IntArray: array	 ;0..4] of integer;
  i: integer;
  s: string;
  IntRec: TIntRec;
begin
  // the array:
  FillChar(IntArray,SizeOf(IntArray),0); // if you comment out this line, you will have random values in the array
  for i := low(IntArray) to high(IntArray) do
    s := s+IntToStr(IntArray	 ;i]);
  form .Caption := 'IntArray: '+s;
  // the record:
  FillChar(IntRec,SizeOf(IntRec),0); // if you comment out this line, you will have random values in the record
  form .Caption := form .Caption+' '+'IntRec: '+IntToStr(IntRec.i )+IntToStr(IntRec.i2)+IntToStr(IntRec.i3)+IntToStr(IntRec.i4)+IntToStr(IntRec.i5);
end;