Kalkulator is a powerful yet simple
to use calculator
and numerical Swiss army knife for Windows (95..XP), with features making it especially suitable for scientific and engineering users, including students of these disciplines.
Anyone with some knowledge of programming can write a calculator program and call it "ultimate" or "professional". And, sadly, almost everyone does that, with results ranging from mediocre to pathetic, but still accompanied with all inflated claims of being "greatest", "most powerful" and whatever.