Calcoo is a scientific calculator designed to provide maximum
usability.  The features that make Calcoo better than (at least some)
other calculator programs are:

* Bitmapped button labels and display digits to improve readability.
* No double-function buttons.
* Undo/redo buttons.
* Copy/paste interaction with X clipboard.
* Both RPN (reverse Polish notation) and "standard" modes are available.
* Tick marks to separate thousands.                                  

Below are the features that Calcoo lacks (but which are useless anyway):

* Statistical mode.
* HEX mode.

WWW: http://calcoo.sourceforge.net/