Re: HP entry methods--please enlighten me Message #5 Posted by bill platt on 25 Mar 2012, 3:33 p.m., in response to message #1 by Matt Agajanian
There aren't different names.
20s is quite different from 27s.
20s has a SWAP and a LAST function. It carries two operating registers. The "INPUT" allows two number regression statistics to be easily entered.
This SWAP makes it possible to correct an inverse or reciprocal on the fly, e.g. 9 / 5 SWAP = 0.555555.
It also allows two independent calcs to be carried out, e.g. 4+5=20 SWAP 6*90=540
SWAP will allow you to toggle. Get LAST in there and you mess it up. LAST is a bit different from LASTX in RPN.
LAST takes the last answer into the current calc, e.g. 4+5=20; 9 X 9 + LAST = 101.
Note that LAST contenst survive when turning machine off, but the "x" register clears to zero.
27S has a LAST but not a SWAP. It has a STACK with 4 levels. You cannot change the order of the stack (darn!) but you can recall rotate it and use whatever happens to be on the level above you (LAST). Yo ucan either CLEAR the current line and get to what is on the upper line, or you can just start a calc, with what you want to use as LAST sitting on the lower line.
27S performs intermediate calculations as you go along and puts that result on the line but does not add if there is a pending operation--but shows the addend on the line. The 21S carries out intermediates as well, holding pending, but does not show the addend. It is more "classic Ti" to my feeling (SR40? I think that's the one I knew as a kid the best).
33s has its own flavor. 35s has the fully "INFIX" version.
20s, 27s and 33s all have Postfix for most or all one number functions (sin cos log etc) but infix for arithmetic. Two number functions vary: some machines utilize the "input" and others (33s) do not. y^x is usually infix with y^x being the separator.
The reason RPN seems so "LOGICAL" is that because it has been defacto HP only, there has been just about only one way it works (well, there are lots of gotchas in old 70s machines!). "Algebraics" come in many flavors and yo have to know each machine...
Edited: 25 Mar 2012, 3:40 p.m.
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