4allCalc (pmCalc) 4.12A calculator with scientific functions, hex, easy transfer to/from the clipboard (Variable "Z"), detailed error messages, online help. pmCalc does not try to simulate a real calculator; there's an entryfield and a result field; you don't have an = button. pmCalc recalculates the result after every keystroke. You enter a formula like you would in a programming language.
Homepage:
http://www.hypermake.com/english/4allcalc.html