Reverse Polish Notation is NOT exclusively unique to Hewlett Packard Calculators....

What is Reverse Polish Notation?

In the 1920's, the Polish mathematician: Jan Lukasiewicz developed a formal logic system which allowed mathematical expressions to be specified without parentheses by placing the operators before (prefix notation) or after (postfix notation) the operands.

Prefix notation also came to be known as Polish Notation in honor of Lukasiewicz. Hewlett Packard adjusted the postfix notation for it's calculator keyboards, added a stack to hold the operands and functions to reorder the stack. Hewlett Packard dubbed the result Reverse Polish Notation (RPN) also in honor of Lukasiewicz.

On Wedensday, January 3, 2007, These groups: "Hewlett Packard Calculators," "HP41," "HP-41 Calculator Users and Owners," "RPN Calculators," and "HomoProgrammus" were established, and dedicated to Hewlett Packard calculator collectors, users, owners, programmers, or anyone who may have a desire to buy, sell, or trade anything Hewlett Packard. At these URLs:

"http://groups.yahoo.com/group/Hewlett_Packard_Calculators,"
"http://groups.yahoo.com/group/HP_Calculators,"
"http://groups.yahoo.com/group/HP-41_Calculator_Users_and_Owners,"
"http://groups.yahoo.com/group/RPN_Calculators,"
"http://groups.yahoo.com/group/HP41,"
"http://groups.yahoo.com/group/HomoProgrammus."

They're places where anyone may buy, sell, trade, or barter, anything for the HP-41 calculator, the Hewlett Packard IL, or it's peripherals that may help the Hewlett Packard calculator user, owner, programmer, or collector. It's one of six "YaHoo Hewlett Packard calculator Groups" established for the HP-41 by: A_Web_Master@YaHoo.Com, or HomoProgrammus@YaHoo.Com.

Presently there are 56 photos of HP stuff for sale at this URL: http://tech.groups.yahoo.com/group/RPN_Calculators, and 51 pictures at this URL: http://groups.yahoo.com/group/HP41, and 78 Pix at this URL: http://tech.ph.groups.yahoo.com/group/HomoProgrammus.