Okay, [okay] ... I'll be the one to put up his hand and ask "What is Reverse Polish Notation?"
As Pan Wiki says:
"Reverse Polish notation (RPN), also known as Polish postfix notation or simply postfix notation, is a mathematical notation in which operators follow their operands, in contrast to Polish notation (PN), in which operators precede their operands."
https://en.wikipedia.org/wiki/Reverse_Polish_notationMmmmm ... kielbasa
That is to say, with RPN you evaluate expressions using correct mathematical order of operations AND enter the expressions into the calculator
in that order.
With "regular" calculators, you still evaluate mathematically, but enter the expressions as you would write them on a piece of paper.
For example: 2 x (3+4). This is 14. "Regular" entry is 2, x, (,3,+,4,) [no commas, just used here to typographically separate the keystrokes].
In RPN, you would enter [let's see if I remember correctly] (,3,+,4,),x,2.
Whew.