Scientific calculator (GTK+)

 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 - you need to click only one button
    for any operation (except for arc-hyp trigonometric functions)
  - undo/redo buttons
  - both RPN (reverse Polish notation) and algebraic modes
  - copy/paste interaction with X clipboard
  - display tick marks to separate thousands
  - two memory registers with displays
  - displays for Y, Z, and T registers