This is an RPN (Reverse Polish Notation) calculator with many useful features. The RPN expression evaluation is superior to Algebraic. It just takes getting used to. There is a four register stack and ten memory locations for number storage. A preview of the register stack is shown at the lower left corner of the display and is extremely helpful in getting used to RPN.This calculator has many useful functions:1) Normal scientific functions, like trigonometry, logarithmic and others.2) Programmable: Included editor, debugger, and many program control functions.3) A very ingenious parameter converter.4) Has a graphics ability. Can work with linear and parabolic graphics but also can graph equations, calculate integration, zero crossing points and other functions. Has linear regression capability.5) Includes an amortization calculator with ability to export amortization parameters.6) Includes a versatile date calculator.7) Extensive help available and it is context sensitive allowing quick help for any key.8) Programmed to make extensive use of a bluetooth keyboard, if attached.9) Can do matrix calculations. Inverse, multiply, add/subtract and will calculate determinate.In short, this is a very useful calculator and can do complex arithmetic, but it is also very handy at doing just simple arithmetic.