Software by Orefa.com:

Powerful Calculator for Finance, Science, Math, Stats, Unit Conversions, Date and Time Calculations, Numeric Bases, Bit-Level Operations, Complex Numbers, Random Numbers, Prime Numbers, Fractions, Trigonometry, NIST Scientific Constants. Quick Popup Access. Selectable Keypads, Button Size, Font, Display Format. Editable Work Area: Calculate, Annotate Your Work, Change and Repeat Your Calculations, Save to File and Restore. Detailed Help File.

AddUp is a free calculator able to process non-trivial arithmetic expressions such as: -(((1 + 2) * 3)^4)% + 56e-7 / 8 Unlike regular desk calculators where the numbers and operators you provide disappear when you enter the next one, AddUp retains all this information for review in an editable work area. Expressions can be edited and re-calculated if necessary. Results can be saved to a text file.