HP 15c - Manual (Page 32)

32
Section 3
The Automatic Memory Stack,
LAST X, and Data Storage
The Automatic Memory Stack
and Stack Manipulation
HP operating logic is based on a mathematical logic known as ―Polish
Notation,‖ developed by the noted Polish logician Jan Łukasiewicz
(Wookashye'veech) (1878-1956). Conventional algebraic notation places the
algebraic operators between the relevant numbers or variables when
evaluating algebraic expressions. Łukasiewicz’s notation specifies the
operators before the variables. For optimal efficiency of calculator use, HP
applied the convention of specifying (entering) the operators after
specifying (entering) the variable(s). Hence the term "Reverse Polish
Notation" (RPN).
The HP-15C uses RPN to solve complicated calculations in a
straightforward manner, without parentheses or punctuation. It does so by
automatically retaining and returning intermediate results. This system is
implemented through the automatic memory stack and the v key,
minimizing total keystrokes.
The Automatic
Memory Stack Registers
T 0.0000
Z 0.0000
Y 0.0000
X 0.0000 Always displayed
When the HP-15C is in Run mode (no PRGM annunciator displayed), the
number that appears in the display is the number in the X-register.