so why did hp display from the left?


is it because of the default 0.0000 fix 4 style? indeed, why was this adopted rather than suppressed zeros and why 4 when 6 digits (fix 5) would make more sense for engineers working at ppm tolerances.

just curious,


Well, early HP calculators defaulted to fix 2.

My guess is that by starting numbers from the left, they didn't have to shift around the previously entered digit across the screen as more numbers were entered. Perhaps this required less programming or ?

Who knows. They pretty much could do what they wanted early on because there weren't any real standards...they were inventing them!



HP calculators have always left-justified numbers in the display. Even the venerable HP-35 did it. As for why, it probably simplified the microcode of the earliest machines (which had very little ROM and RAM to work with, since it was so expensive). But this is just speculation on my part.

About the fixed number of decimals, the HP-35 was, for a few long yeas, the only one lacking it. Classic HP calculators invariably defaulted to FIX 2 when powered on; if you wanted anything else, you had to start pushing buttons. Then the 41C came out and changed all that to FIX 4.

Actually, I like the fixed display better than the automatic-zero-supression mode (named ALL in some calculators, STD in othes). It makes things consistent. Hey, at least now the calculators switch to scientific notation when the numbers get too small; the earliest HP calculators stayed in FIX 2, displaying a horribly misleading "0.00"!



I meant to add this to my previous post:

Another odd thing about number entry in HP calculators is that multiple leading zeros are accepted and displayed. Virtually all non-HP calculators ignore further presses of the [0] key.

For example, press [0] [0] [7] to get James Bond in the display. Now do that on a Casio or TI. All you'll get is "7."



In one of the Woodstock manuals (HP21 or HP25, I do not remember which one) HP explained that the numbers on the display are entered from the left to the right just because this is the way you would write numbers on paper. Then they continued explaining that RPN system also follows the same way you would calculate on paper, etc.


I'll add that I would suspect numbers from the left side of the display as a recognition that most people are right-handed. If you type with your right hand, which side of the display is more likely to be masked by your hand? And when the new digit goes into the building number, what digit is furthest from any masking effects?

I vaguely remember that there was such a consideration as to the four-banger functions, and that's why the Classic, Woodstock, & Spice series had the functions +-*/ on the left side of the keyboard. What I don't remember is what argument was presented to migrate such over to the right side, Voyagers & Pioneers (& my venerable 48S).



being the unique of its kind, the HP16C shows a right-justified number input when it is in integer mode (HEX, DEC, OCT or BIN). Left-justify input is assumed (like other voyagers) when FLOAT n mode is selected. The HP28 and 48/49 show a different behavior: the numbers are entered in a left-justified command line, but are showed in a right-justified stack level. For all tastes...

I have the original HP25 manual and I found Nenad's (thank you!) valuable observation, on page 14, under Keying In Numbers:

Key in numbers by pressing the number keys in sequence,
just as though you were writing on a piece of paper.
What else to say?


> the HP16C shows a right-justified number input when it is in integer mode

HP-41C can do the same with Advantage module (BININ, OCTIN, HEXIN) ...


The HP16C is not the only one, the HP32Sii also displays non base 10 numbers (BIN,OCT,HEX) as right justified. Actually BIN mode spreads across several screens but normally displays the least significant bits as right hand justified when the number is less than 12 bits long.


Hi, Tom;

if I am not wrong (I used an HP32SII a long time ago...) it showns right justified integers, but left-justifies them when typing them in, right? Input numbers follow the same rule, what they are going to be is up to the user. Is it correct?

If it's correct, the HP32SII acts the same as the HP28/48/49.



HP LED calculators defaulted to FIX 2 mode (meaning 0.00).

Dunno about HP11C/15C, etc but the HP41C/V/X calc defaulted to 0.0000.

With limited ROM space in the first HP calcs (35, etc.) the code required to do floating display, etc may have been regarded as superfluous - and may have included HP design engineer's sense of significant figures (why carry a given calc out to N places if lots of your data is only good to 2 or 3 places, for example).

Also, on an LED display calc, defaulting to FIX 2 also saves battery life over displaying in FIX 4.

[ An aside: If you've ever seen the library source code for the C function printf() you know that this is a fairly 'large' function compared to many others in libc, and the formatting code takes quite some space. In fact, on current C compilers targeted to small 8-bit embedded processors, there are sometimes several versions of the printf() function that can be linked to your code, with some having quite a few features removed (in many cases, floating point formatting) and consequently saving a few KB of ROM after linking. ]

Bill Wiese
San Jose, CA

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