Hewlett-Packard HP-35s scientific calculator

I am a diehard RPN and HP calculator fan. I bought this calculator for the PE exam. HP calculators I've owned include HP41c, HP42s, HP12c, HP17BII, HP19BII, and HP33s. The HP35s is basically an HP33s with most the ergonomic design flaws and quality issues of the HP33s fixed, along with a few added enhancements. It's what the HP33s should have been in the first place. But, along the way, it also introduces a few design flaws of its own.

Obvious pluses: The keys on the HP35s feel almost like the ultra high quality keys on the HP41c, not entirely there because the ones on the HP35s are flatter and have less travel distance, but very close. However, unlike those on the HP41c, some of the secondary colors on the keys are only painted on. How long would the paints last? It comes with a super nice semi-rigid vinyl case. The LCD display is fragile, but it seems to be dust-proof and has excellent contrast. The built-in metric/imperial conversions and constants library are also nice. One major enhancement over the HP33s is the ability for a program to refer to a line number instead of a label name during conditional branching. This feature allows the writing of programs that don't use up a lot of the precious program labels. The equation solver is quite powerful. It comes with built-in equations for solving 2x2 or 3x3 simultaneous equations.

Obvious minuses:

There are only 26 single alphabet program labels and only 26 variables, severely limiting the number of programs one can store, considering the somewhat large 30kB memory available(the HP42s only has 8kB). The manual has a good number of useful programs, but in reality one can store only a few of these programs on the calculator at a time due to the 26 program label limit. I can store more programs on the HP42s even though it only has 8kB of memory. In actual use, most of the 30kB on the HP35s will go untapped.

It's a shame HP chose not to include multi-letter alpha-numeric capability as they did on the HP41c and HP42s. Instead of labeling a program that calculates the time value of money using a single letter such as "T", I'd much rather be calling the program "TVM" or "MONEY" or something easy to remember. The same one-letter restriction applies also to variable names. The listed battery life is on the short side. Two hours of use per day will last the batteries only about 9 months.

Whereas the HP42s offers four types of curve-fitting and has capability to choose one with the best fit, the HP35s offers only linear regression. Also, unlike the HP42s, the HP35s doesn't have any built-in matrix capability to evaluate determinants, inverses, although it does have built-in 2x2 or 3x3 simultaneous equation solving ability as mentioned earlier. You can program all these missing capabilities in but you'll use up many of the precious 26 program labels in a hurry.

The STO key which I use very often is now subordinated, requiring a shift key, whereas the "Mode" key which I seldom use is primary.

The display has much more glare than other HP models I've owned.

Although I will almost never use the algebraic mode except when writing equations, I must mention that its implementation on the HP35s is clumsy. On other algebraic calculators I grew up with, the number precedes a function key (such as COS, 1/x, log) and the function is executed as soon as the function key is pressed. In other words, even though they are algebraic calculators, their function keys work in postfix or RPN mode.

The key sequence is

45

COS

The value of 0.707 is displayed as soon as the COS key is pressed. It's very simple and intuitive. This is also how the functions work on the HP33s. But, surprise, this ain't how it works on the HP35s!

On the HP35s, you have to start by first pressing the function key and then punch in the number and then press the Enter key to get the value.

The key sequence is

COS

45

ENTER

The ENTER key works as the equal sign key in algebraic mode on the HP35s. Hitting the ENTER key now becomes mandatory to get an answer from just about any operation. Although this peculiar algebraic approach may make sense when writing equations, it's highly cumbersome when doing calculations on the fly, especially for someone used to the keystroke efficiency of RPN.

I sometimes scratch my head trying to figure out why for the last 10-15 years HP kept churning out mediocre calculators, with each new one worse than the previous one. Why mess with winning designs and dumb them down to the level of TIs and Casios? Yes, the money is where the masses are and the masses are the high school and college crowd and they use predominantly TIs and Casios. Then it dawned on me that the sales execs, designers, programmers, engineers also have to somehow justify their existence by rolling out new models and discontinuing older but superior models. The HP35s seems to be a step to halt the march toward mediocrity. Does it succeed? Yes, mostly. Although the build quality is good, it certainly could have been designed better.

Even though the STO key is now subordinated, the HP35s fills the need for basic everyday number crunching due to its ergonomic form factor and ease of use combined with a reasonably rich set of functions. The HP50g fills the need for heavyduty scientific/engineering use but is too clumsy for everyday basic number crunching.

I'm sure as I use this calculator more, I will see more of both the pluses and minuses. And, if I were to rate this calculator in comparison with any Casio or any TI, I would give it 10 stars if I could. But I rate it in relation to what I expect an HP calculator should be and so I rate it 4 stars. If the HP35s came with more program labels and variables than just 26 of each (A to Z), multi-letter alpha-numeric data entry capability, matrix capability up to [5x5], 4 types of curve fits and best of fit, primary STO and RCL keys, I would rate it 5 stars.