|RPN||Reverse Polish Notation, postfix
As opposed to the Adam - Riese notation with * / precedence over + - and the use of
parentheses, the RPN only uses COMMANDS.
It is also well known as the STACK OPERATING notation and the ENTER notation,
as introduced 30 years ago by Hewlett Packard with the HP-35 handheld calculator.
|IS EASY!||Using RPN is surprisingly easy, there are virtually
no rules to learn, except one:
the order of actions (commands) is the only important issue.
The calculator is ideal for engineers and scientists for small online calculations. The
program is so small and does not waste resources, so that you can leave it on the
Windows desktop all the day. While calculating you get all intermediate results
visible on the stack, so you can prove the validity of your "algorithm" on the fly.
All commands can be entered with the mouse, most with the keyboard too. It will
need a few minutes of training only to use the RPN calculator economically.
|COMMANDS||Saying that RPN uses COMMANDS means that there is
no distinction between
operators and operands, because there are no operators and no operands. Even the
number entry can be treated as a command: put nnn on the stack!
+ and - and * and / are no operators in RPN, they are commands. The user should
treat them as mnemonics only for the commands "add!", "subtract!", "multiply!", "divide!".
There are several housekeeping commands to manipulate the cells on the stack,
DUP and SWAP, OVER and DROP etc.
You should treat the stack as a stack of small paper sheets, containing one number
each and lying on the desktop. One cell is the top cell, the TOS (top of stack), next is
It is typical for the RPN that variables are unnamed (as opposed to usual programming
practices), they are solely referred to by their position on the stack.
but in many cases it is not necessary to press Enter, it is automatically performed by
the following command, it is built-in in the command.
The ! command can also store the value of the selected (mouse) stack cell to a
register, and ^Ins works on the selected cell too. If no cell is selected, TOS is
|REGISTER||The register is a small array to store 10 numbers for later use. Usually
to calculate with are on the stack, it is deep enough and you have commands to
copy any stack location to TOS.
continue your work next morning.
Some users will notice that the mnemonics are derived from the FORTH
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