Path: utzoo!news-server.csri.toronto.edu!rutgers!dimacs.rutgers.edu!mips!news.cs.indiana.edu!rsg1.er.usgs.gov!rsg1.er.usgs.gov!stevev From: stevev@greylady.uoregon.edu (Steve VanDevender) Newsgroups: comp.sys.handhelds Subject: Re: RPN intuitive? Message-ID: Date: 14 Mar 91 06:55:04 GMT References: <7645@mentor.cc.purdue.edu> <1991Mar12.014121.925@csn.org> Sender: news@rsg1.er.usgs.gov Organization: University of Oregon Chemistry Stores Lines: 43 In-Reply-To: bob@dolores.Stanford.EDU's message of 12 Mar 91 02:29:26 GMT In article bob@dolores.Stanford.EDU (Bob Lodenkamper) writes: Remember the older RPN calculators only displayed the x register, and I see little difference between having to remember what's on the stack and putting in all the silly parentheses required by an algebraic calculator. The 4 line display may be the single most useful innovation introduced in the 28. - Bob I have one of the oldest HP calculators, an HP 9100A. It has only a three-level stack, but displays all three stack registers. There's even a small lighted sign next to the CRT that labels each register: --------------------------------------- | -8.888 888 888 -88 | z temporary | | -8.888 888 888 -88 | y accumulator | | -8.888 888 888 -88 | x keyboard | --------------------------------------- So a labeled multi-level stack display isn't THAT new. The 9100A also has RPN a little different from its successors, in that stack lift and stack drop are not automatic (although there are keys for doing either). All input goes into the x-register, overwriting its original contents. +, -, *, and / operate on x and y and return the result to y, leaving x and z intact. Most functions of one argument operate on x and return a result to x, except for |y| (now known as ABS), which takes the absolute value of y and returns it to y. The 9100A also has the original form of synthetic programming--the program and data registers are not partitioned so it is possible to make self-modifying programs. Since the 9100A does not have subroutine calls, this was undoubtedly used to advantage in some circumstances. -- Steve VanDevender stevev@greylady.uoregon.edu "Bipedalism--an unrecognized disease affecting over 99% of the population. Symptoms include lack of traffic sense, slow rate of travel, and the classic, easily recognized behavior known as walking."