HP 50g Graphing Calculator

Why I Like the 50g* The ControversyIf you google "TI v. HP" you can find dozens of discussions by partisans of both brands ofcalculators arguing for the relative merits of the their favorite model. These days, the two modelsunder discussion are the TI-89 from Texas Instruments and the HP-50g from Hewlett-Packard. Almostinevitably, the discussion goes straight into whether the Algebraic or RPN entry method is better.I can summarize the argument pretty quickly: "RPN saves one or two keystrokes." "Maybe, butAlgebraic is easier to learn---it's just like the way you would write it." From there, someone mightmention the number of built in functions for each, 850 versus 820, or the speed of solving anintegral, 1.2 versus 1.1 seconds.I find these arguments almost completely irrelevant to the things that draw me to a calculator, andI tire at their repetition. I will put my cards on the table right now. I far prefer the HP50g forreasons I will discuss in a second. I own a TI-89 and the really cooler TI-92 plus with the fullalphabetic keyboard, and they are both fantastic calculators. But the HP-50g is "fun" in a waythat's hard to explain in a post. It is *not* RPN, or at least not RPN in isolation from the wholeecosystem of the HP-50g, that makes it fun.* The StackI don't know why but the HP's stack hardly ever figures into these discussions, yet to me, it is theindispensable facility of the HP-50g that gives it its elegance. You probably have some idea of whata stack is, but if you don't the concept is easy, but powerful. The stack is a pile of numbers thatsit on the calculator that can be removed only from the "top" of the stack, which in the HP isactually displayed at the bottom. Here, for example, is what the stack might look at somewhere inthe middle of a calculation:7:6:5:4:3: 52: 3.51: 9The number 9 is on the "top" of the stack, position "1", labeled at the left. Further up the stackare 3.5 and 5, while the rest of the stack is empty. If I enter another number, say, 6.7, it gets"pushed" onto the top of the stack and all the other numbers get bumped up into the next higherposition. Like this:7:6:5:4: 53: 3.52: 91: 6.7The stack serves as a kind of universal input-output facility for the calculator. All of thefunctions, and I mean *all* the functions, take arguments from the stack and---here's the importantpart---they push their results back onto the stack, starting at position 1, the "top."The '-' key, for example performs subtraction, a function that takes two arguments. Where does itget its arguments from? The top two numbers on the stack, of course. And it applies thesubtraction to them in the same order that you see them, in this case it will compute '9 - 6.7'.Where will it put the result, 2.3? On the top of the stack, of course. After pushing the '-' key,the stack becomes:7:6:5:4:3: 52: 3.51: 2.3This regular, predictable behavior gives the HP50g an interactive feel that allows you to "play"with the numbers more that CALCULATE. You're not Spock, after all, you probably want to fiddle witha problem a bit. You can stop, contemplate, perform a side calculation, and when you're done, thestack will return to where it was when you left off the main problem. Say you have 45 on the stack,and are thinking of taking its sine. As you ponder the problem, you realize that you really wantthat 45, which you've been regarding as degrees, converted to radians before you take its sine.These sorts of mid-course corrections are just what the stack is made for. You remember that to getthis done, you have to divide by 180, then multiply by pi. Simple, just enter 180 / pi *, and you'vegot your radians. Now you can get back to the problem of taking the sine (just press the [SIN] key,and there it is on the stack for you to think about and operate on further.The stack on the HP-50g (and the 49g and the 48g and the 28s, etc) has an unlimited depth, so youcan push numbers onto it to whatever depth the problem at hand requires up to the limit of availablememory, and I for one, have never found the end of memory on the 50g. This contrasts with earlierHP's that had a stack that was limited to 4 numbers, usually with only two of them visible. On the50g, up to seven elements are visible, and you can look at the rest by hitting the cursor key to goup as far as your curiosity takes you. The TI calculators don't have a stack. They have a history,which is nice, it allows you to go up and re-enter an expression, but it lacks that spontaneouspush-pop play of the stack.* Now RPNDon't get me wrong, RPN---Reverse Polish Notation---is a great way to think about numbers andoperating on them. But all by itself, it's just a bit more efficient in keystroke count (who cares,already!) and strikes many people (as it did me) as a kind of backwards way of looking at aproblem. But, when combined with the stack, you really get to understand the power andexpressiveness of the RPN way of operating on numbers.To get into the spirit of RPN, it helps to first understand PN, Polish Notation. Consider thefollowing nested expression:SIN(3 * 8 - COS(4 / 7)) - 17This is in normal, algebraic form, pretty much just like you would enter it into a TI calculator.But the expression can be rewritten so that every operation is regarded as a function that is placedin front of its operators in parentheses, just like we do already with functions like sin(x), wherethe function name goes in front of its parenthesized argument. But in Polish Notation, even thingslike '+' and '-' are regarded as functions, so that '3+2' would be written '+(3, 2)'. Now, if were-write the above expression this way, we get this:-(SIN( -( *(3, 8), COS( /(4, 7)))), 17)That's Polish Notation, or prefix notation. Each function is written at the front of theparentheses that surround its arguments. The idea of Reverse Polish Notation is that the functioncould go *after* the parentheses that surround its arguments just as well. So, '3+2' could bewritten '(3,2)+'. Now, our complicated expression looks like this:((((3, 8)*, ((4, 7)/)COS)-)SIN, 17)-Now here, finally, is the punch line. Using this Reverse Polish, or postfix, notation, we can eraseall the commas and all the parentheses:3 8 * 4 7 / COS - SIN 17 -As long as we (and the calculator) know how many arguments each function takes, this expression iscompletely unambiguous. With algebraic notation, we needed parentheses to specify the order ofoperations. As it turns out, *any* expression can be written in RPN without parentheses to specifythe order of operations and without any ambiguity. Furthermore, we can enter the expression strictlyleft-to-right.But the real pay-off is that this notation is perfectly suited to working with the stack. See, wepush 3 and 8 onto the stack then press '*', which pops 3 and 8 from the stack and pushes 24 onto thestack. Then we push 4 and 7 onto the stack, hit the divide key, and the 4 and 7 get popped from thestack while 0.571428571429 gets pushed onto the stack. Hit COS, and 0.999950266956 goes onto thestack (replacing the 0.57...), and our 24 gets pushed up. Then, '-' gives 23.000049733, SIN gives0.390731927492, we push 17, then '-' and -16.6092680725 is sitting on the stack ready for anyfurther calculation.Yes, yes, the RPN notation is only 11 keystrokes, while the algebraic is 15, saving a whopping 4keystrokes, all parentheses and commas, but that's not the beauty of RPN. RPN shines because itworks with the stack, and the stack gives you a visible, interactive, and universal mechanism forreading inputs and writing outputs. Only the HP calculators sport this combination of a stack andRPN.* Elegant ProgrammingHaving a stack and a notation that takes advantage of it were enough to sell me on the HP-50g all bythemselves. But, since both the HP-50g and the TI-89 are *programmable* calculators, it is reallyimportant to know what kind of programming environment each provides. Here is where the HP reallyrockets ahead. I have owned both calculators for many years, and I've spent many hours programmingthe HP, but almost none with the TI's. Why? Well, the HP provides a language and facilities thatmake programming the thing a pleasure. It's language is called "User RPL," and the RPL stands for"Reverse Polish Lisp," but it is really more reminiscent of FORTH than Lisp.An RPL program, in its simplest form, consists of a series of commands enclosed in guillemots, thosefunny foreign quote characters that look like this '<< >>'. With a single keystroke, I getthese delimiters placed in the command-line with the cursor conveniently placed between them, readyto enter the program. The best thing about the HP-50g's programming language is that every programby default works with the stack exactly as you do when doing regular arithmetic. Let's say forexample, that you want to work out the hypotenuse of a right triangle given the lengths of the twoshort sides using the Pythagorean Theorem. If 'a' and 'b' are the lengths of the two given sides,the hypotenuse has a length equal to 'SQRT(a^2 + b^2)'. What's nice about programming the HP is thatI write my program assuming that the two input numbers, a and b, are sitting on the stack. Then, Ijust enter the program like this:<< [x^2] [SWAP] [x^2] + [SQRT] >>The [brackets] denotes a single keystroke on the calculator, thus [x^2] is the squaring key, [SQRT],the square root key. [SWAP] swaps the order of the two numbers on the stack. Having entered thislittle program, I hit [ENTER] and it goes onto the stack, just like numbers do. Then I can enter aname on the stack, say 'HYP', and hit the [STO] key, and my little program now has the name HYP. IfI put 3 4 on the stack and hit HYP, I get 5 on the stack, just as Pythagoras said I would.There's a whole lot more to programming than this, but this little thing exemplifies the how easy itis to do "quick and dirty" programs and put them to work right away. The input-output facility ofthe stack keeps me from having to worry about where the arguments come from and where they go to.No blabby prompts to worry about to get the two arguments. And because it uses the stack, thislittle program becomes an extension to the built-in facilities of the calculator that I can use inthe middle of a longer calculation. In fact, it can become a small part of a much larger program.User RPL also has if-then constructions, while- and for-loops, error traps, dialog boxes, and allthe other paraphernalia you expect from a decent programming language. But for me, the ability toquickly crank out little stack-based programs is where the HP-50g really shines.The TI-89 also provides an editor and an environment for writing programs, but the language is morelike BASIC. It requires keywords, like Function and Program, declaration of local variables, and soforth. The language feels ponderous and more "computer" like than the nimbleness of the HP.Oh, and I almost forgot. The HP has a debugger that allows you to single-step through your programswhen they don't do what you think they should. You can actually watch the stack do its thing duringthe execution of a program. This is really handy. And oddly fun.* Single-key operationI skirted over an issue, and a really important one, in that last section. I said I could put 3 4on the stack and "hit" HYP to get a 5. But there is no HYP key on the HP-50g. Or is there? Well,there is. There is a [VAR] key that causes a menu of "soft keys" to appear on the bottom of thescreen below the stack with the names of all the variables I've created with the [STO] key. If Ihave stored a program in the variable, I can run the program by hitting the key underneath the HYPsoft key label. If I've stored a number in a variable, I can put that number on the stack bypushing its soft key.This means I can run the program with a single keystroke. You can see up to six variables in thesoft key menus and page through the rest, six at a time, by hitting the [NXT] key. So I have singlekeystroke access to every variable. There is never a need to use the [RCL] command. No need toretype HYP every time I want to use it. By contrast, on the TI, I can write a program called HYP,but when I want to invoke it, I have to type H-Y-P-(-3-,-4-). That's eight keystrokes to three (3 4HYP) on the HP. As little as I think of the keystroke efficiency argument in discussing RPN versusalgebraic, this *is* a BIG DEAL. What if the name were 'HYPOTENUSE'? Still one key on the HP; youcan count 'em for yourself on the TI.In addition, the HP lets you assign programs to *any* key on the keyboard using any combination ofunshifted, left-shifted, right-shifted, and more. This makes any program accessible whether thesoft-key menus are showing or not.* Directory StructureHere's another well-thought-out feature of the HP-50g: it's clever implementation of directories.The calculator's memory is organized into a tree-structured set of directories, with a directorycalled HOME at the top. You can create directories under HOME, and directories under those, and soon as deep as you like. These directories are like the directories on a computer, but the "files"are variables. This provides a nice, easy way to organize your work. When you start out on a longproblem, the first thing you should do is create a directory for your work. This keeps all yourvariables from conflicting with variables of the same name you might have used for other problems.Furthermore, when you are working in a directory, all the variables in that directory are availablefor use as well as all the variables in every directory between your current directory and HOME atthe root of the tree. So the variables in the HOME directory are global, while each subdirectoryunder it creates a kind of nested name-space below it. This setup is easy to understand and allowsyou to create whole branches of memory that share common programs for a given problem area.But that's not all. In each directory you can create a variable called 'CST' that allows you tocreate a customized "soft key" menu for just that directory. This is in addition to the 'VAR' menuyou get in every directory for free.* The SD CardFinally, the HP-50g supports the insertion of an SD card. My calculator has a 1GB card, which Iwill never fill. It also has a USB cable, like the TI, for transferring files to and from yourcomputer, but I find having an SD card reader attached to my computer makes transfers really easy.It won't run programs directly from the SD, but it makes for an excellent backup for your wholedirectory structure, and from there you can backup to your computer.

This is a review of the HP 50g Graphing Calculator by Hewlett Packard. If you are (or aspire to become) an engineer, mathematician, physicist, or physical chemist, then this is the calculator for you. Actually, this is not really a calculator: it is a hand-held math computer with a calculator-style human-machine interface. The capabilities of this math computer are mind boggling.Right up front, please note: the HP 50g is NOT allowed on the Fundamentals of Engineering (FE) exam. If you want a calculator for the FE exam, try the HP 35S (HP 35s Scientific Calculator). Refer to the NCEES website (search for calculator policy).I have used Hewlett Packard calculators for years. While it is true that the HP 50g build-quality is not as robust as previous models, and while it is true that there have been some disappointing design changes, this calculator still amazes me. It is incredible that it sells for such a low price. By the way, my favorite calculator was my old HP 28S (too bad the case cracked at the battery door). I also have owned (and have extensively used) the HP 48 and the HP 49g+ (not to mention the HP 15 and HP 35).There is nothing wrong with Texas Instrument (TI) calculators. In fact, they are quite great. However, once you get used to the Reverse Polish Notation (RPN) of the HP 50g, you will be able to perform calculations much faster than with a TI. If you are still in high school, then you might want to check with your university before buying a calculator. Some college programs require (or endorse) a specific calculator model, and integrate use of that model in the course(s).The HP 50g is for folks who perform relatively high-level math. To use the capabilities of the HP 50g, you need to complete college calculus, vectors, differential equations, linear algebra, control theory, and statistics (and more). This calculator is ideal for college students who major in math, statistics, physics, chemistry, or engineering. Other users will NEVER use most of the functions of this calculator; in fact, most of the folks I know who own an HP 50g only use its most basic functions (what a waste). Unless you are going to use advance mathematics, then you might be happier with an HP 35S.This calculator has over 2300 built-in functions. While this is quite impressive, jamming so many functions into this calculator makes operating it much more challenging than (perhaps) it needs to be. Some of the handy features of the HP 50g include: the equation writer, the matrix writer, a constants library, an equation library, units conversion, interactive graphs, libraries, and (of course) programming (many folks share their programs free).It takes a very long time to learn how to use this calculator. In days of yore, Hewlett Packard would ship wonderful (spiral-bound) books with each calculator which explained in clear, perfect detail how to use each and every function. Such a manual for HP 50g would probably run 3000 pages and would surely double the price of the calculator. Hewlett Packard does provide three documents for the calculator: (1) a 184 page "User's Manual," and (2) an 887 page "User's Guide," and (3) a 693 page "Advanced User's Reference Manual." A hard-copy of the "User's Manual" might ship with the calculator; the "User's Guide" might be included on a CD included with the calculator. In any case, be sure to visit the Hewlett Packard website and download the latest (perhaps, corrected) copies of these manuals. While there, also download the latest USB driver for your operating system.After you first receive your new HP 50g, set aside an hour per day to learn how to use it. It will probably take you at least 100 hours (maybe 40 hours for the most important operations), even if you are already a math whiz. While HP no longer provides adequate training documents, you can find some good tutorials online. For example, search university websites (*.edu) for HP 50g tutorials (e.g., Thiel college). (Please note, the HP 49g is so similar, tutorials for the HP 49g will help you too.) Look on you tube for HP 50g tutorials (one fellow in particular has posted a series of great videos). Go through a textbook (one you've already completed, or one you are going to use next semester) and get practice entering equations and solving problems.If you have the cash, check out the following books by Gilberto Urroz: Science and Engineering Mathematics with the HP 49 G - Volume 1 (Gu) and Science and Engineering Mathematics with the HP 49 G - Volume II - Calculus, differential equations, statistics. They were not written specifically for the HP 50g, but the HP 49g and the HP 50g are almost identical. I bought both books. They are pretty good, but you should try out Volume I before you buy Volume II (just to make sure it meets your needs).Here are some extra items you should get at the time you buy this calculator:- At least two 1 GB or 2 GB SD cards.- A fresh CR2032 battery.- 8 rechargeable AAA batteries (and charger, if you don't have one).- A mini-B USB cable (if one is not provided with the calculator).Explanations:- An SD card (Transcend 2 GB SD Flash Memory Card (TS2GSDC)) can be installed in the bottom of the calculator. You can then backup your calculator to the SD card by copying files and entire directories to the card. Trust me: You MUST backup your calculator. You may eventually have hundreds of hours invested in storing equations and programs in your calculator; you do NOT want to lose all that hard work if your calculator loses power or if it is damaged or stolen. With the calculator backed up, you can easily restore your directories, equations, and programs (to a replacement calculator, if need be). You should have at least TWO SD cards, so you can have one installed, and one in a safe location. An SDHC card will NOT work, it must be an SD card (therefore, limited to 1 GB or 2 GB). Install this card on Day 1, and format it for FAT16 (not FAT32).- The calculator comes with a CR2032 battery; but I recommend installing a fresh (high capacity) battery on Day 1. This battery is used to backup the calculator's memory.- This calculator eats batteries. Do yourself a favor and buy two sets of rechargeable AAA batteries (8 total) Sanyo NEW 1500 eneloop 4 Pack AAA Ni-MH Pre-Charged Rechargeable Batteries. However, please note the following guidance from Hewlett Packard "The use of rechargeable batteries is not recommended because of their lower capacity and short low-battery warning."- A USB mini-B cable should come with the calculator (Connectivity Kit). If you need to buy a cable, then buy it NOW so you can connect your HP 50G to your computer. Go to the HP website, then download and install the latest HP 50g (USB) driver for your operating system. Search the web for a copy of the connectivity software (Conn4X) and install it. Search the web for instructions on how to establish communication between the HP 50g and the connectivity software. This will allow you to backup your HP 50g to your computer. Later, if need be, you can restore your calculator, or you can load the files to a new, different calculator. After you spend hundreds of hours loading equations and programs into your HP 50g, you really (really) want to have a backup. Also, if you have a USB cable, you can ensure power is maintained to the calculator during battery changes by plugging the calculator into a powered USB port.I repeat: Learn how to backup your HP 50g (to SD card, a computer, or both). If your calculator loses power or locks up and needs to be reset, you can restore all of your directories, equations, and programs from backup. Also, if your calculator is stolen, breaks, or fails, having a backup (on computer, or a safely-stored SD card) will allow you to reload your new (replacement) HP 50g just like the old one. Also, backups will allow you to transfer directories and their contents to a friend's HP 50g.Recommendations for Day 1 (i.e., when you first receive your HP 50g):- Change KEYTIME parameter to 1138 (some folks say, set KEYTIME to 500). If you don't do this, then the calculator may not accept repeating numbers if they are entered very quickly. For example, if you enter 111 very quickly, the calculator might only enter 1. Here's how: [ALPHA] [ALPHA] 1138 [RIGHT ARROW] -> KEYTIME [ENTER]. -> represents the character over the 0 key (press right-shift key, then 0). If you want a KEYTIME of 500, then substitute 500 (instead of 1138) in the above entry.- Find the you tube video for HP 50g setup (My Setup for the HP-50g) and watch it. Change your setup as you like (by using the MODE menu and by setting FLAGS).- Figure out how to set up directories (aka, folders). For example, if you are in college, you will probably want a different folder for each department, with sub-folders for each course, with (maybe) sub-sub-folders for each chapter. For goodness sake, do NOT enter all of your equations into the HOME directory. If you are a working engineer, then you might want a separate folder for each work order.- Go to Appendix B of the "User's Guide" and review the keyboard, paying particular attention to the key-functions that are NOT labeled on the calculator (this makes me SO mad!). For example, greek letters are not labeled, nor are the keys for angle (when in polar coordinates) or factorial (!). Likewise, all of the following are not labeled: edit function, SWAP function, switching between exact and approximate, switching between real and complex, entering equation editor for an equation on the stack. Also, I am very annoyed that the equation library and the constants library are not directly available from the keyboard (you must use the APPS key or the CAT key).- Discover functions available via the APPS key (column 1, row 2). Some of these functions are also available directly accessible via the keyboard (e.g., equation writer, matrix writer, math menu), but some are not (e.g., equation library and constants library).- Learn how to PURGE variables. In the past, Hewlett Packard calculators had a dedicated PURGE key; but now the PURGE function is (stupidly) hidden as a sub-menu item. If you do not know how to PURGE variables, then your directories will become hopelessly cluttered with old, discarded variables.Hewlett Packard also makes emulators for all of their calculators that can simulate the calculator on a computer. You tube has tutorial videos for the HP 50g that illustrate use of such an emulator. I also use several computer-based programs that you might want to check out: Mathematica, Stella, and SAS.I have written this review with the college student in mind; but (obviously) this calculator is also ideal for professional engineers and scientists.Update (12/11/12): Also check out The HP 50g Calculator Tutor (Hewlett Packard).