function TfrmPWGenerate.btnGenerateClick(Sender: TObject): string;

{max length of generated password}
const
  intMAX_PW_LEN = 10;
var
  i: Byte;
  s: string;
begin
  {if you want to use the ‘A..Z‘ characters}
  if cbAZ.Checked then
    s := ‘ABCDEFGHIJKLMNOPQRSTUVWXYZ‘
  else
    s := ‘‘;

  {if you want to use the ‘a..z‘ characters}
  if cbAZSmall.Checked then
    s := s + ‘abcdefghijklmnopqrstuvwxyz‘;

  {if you want to use the ‘0..9‘ characters}
  if cb09.Checked then
    s := s + ‘0123456789‘;
  if s = ‘‘ then exit;

  Result := ‘‘;
  for i := 0 to intMAX_PW_LEN-1 do
    Result := Result + s[Random(Length(s)-1)+1];
end;

initialization
  Randomize;

结果:
IBbfA1mVK2
tmuXIuQJV5
oNEY1cF6xB
flIUhfdIui
mxaK71dJaq
B0YTqxdaLh
...