HP 50G or TI89 I'm an engineering student looking at buying one of these 2 calculators. I've been using a TI83, and one of my professors strongly recommended getting a TI 89 (or similar) for my more advanced classes. I've got no problem learning RPN, but I've only fiddled around with it a little on a basic scientific calculator. One of the things I love on my TI83 is that I can have the calculator retype for me a calculation I just used in case I need to change something, like adding parenthesis, or changing plus to minus so I don't have to retype the entire quadratic formula, etc. I can't see how this would work in RPN. Any thoughts?
I can see how you might get used to that way of working, on modern algebraic calculators. The 50G in algebraic mode saves all your calculation inputs in a history. I believe late TI's do the same. You can just pick the expression from history and edit it. ...Course we prefer RPN mode on 50G. There many corresponding possibilities. They do need you to know in advance, though. Normally one would either input the RPN sequence in << ... >> or the algebraic expression in ' ... ' and duplicate it on the stack or save it as a var. It can then be edited and EVAL'ed as you desire. Normally though, one would represent those values, one intend to vary, with symbolic variabel names instead, like A, B, C whatever, and store values under those variable names. The << ... >> sequence is actually a program, btw, and will execute as you press the soft key representing the name you stored it under. The basic answer to your question is that one would store some kind of program. How exactly to do that and how to make it take parameters, is something that has many, many different possibilities. The RPN/RPL system is very flexible.
The HP 50G is a superior working tool. For studies though, I think you may need to consider if it's allowed for exams? I think 50G isn't much? since it's an all-out tool. TI calculators typically are. They are adapted to different exam levels. But for your professional companion, you don't want algebraic or TI. You should get HP's most advanced model with RPN/RPL. Currently that is the 50G.
I own two HP50g calculators, and use them in the postfix RPN mode, but a former coworker of mine had the original TI-89, and in its probable 'home screen' there were file-folder-like structures, with tiny labels so pixelated they were quite tough to even read. That isn't so using the HP50g in prefix-infix 'algebraic' mode. There is just a screen there you calculate. Plus there is an elegant programming language called 'User RPL' in the 50g, but only some kind of program editor in the TI-89, and I have seen the latter in the TI-89 PDF manual.