How old is the segmented digit display?

[brouhaha]

Anyone want to hazard a guess?

Today I heard of an older one than I'd previously heard of. I'll reveal it later today. Those of you who also learned of it today might want to not reveal it just yet, so we can see what other forum members thing.

[lvt]

Do digital watches count?

[Paul Dale]

1903 Carl Kinsley?

   

[brouhaha]

(12-03-2023 03:46 AM)lvt Wrote:  Do digital watches count?

Sure.

[brouhaha]

(12-03-2023 04:04 AM)Paul Dale Wrote:  1903 Carl Kinsley?

That's earlier than the one I learned about, which was F..W. Wood in 1908, with an eight-segment display (one diagonal segment used to make the "4" nicer).

I see that both are listed in the Wikipedia article "Seven-segment display".

[johanw]

(12-03-2023 03:46 AM)lvt Wrote:  Do digital watches count?

The first digital watches were mechanical ones, with the hour and minutes displayed with rings like the date and day of the week on current analog watches.

[Johnh]

Really interesting to see that the concepts for these displays were in place so early last century! There's something really clear about a good 7-segment display for displaying numbers, better than most dot matrix or more complex versions, up until you can do a really bright high-def display. Also, those 7 segments need minimal electronics to manage. Just for our calculators, the 7-segments look the best for when only digits are needed.

Sadly, when you try to make them do letters too, there are several letters that just don't have a very credible option, even if a mix of upper and lower case is accepted. M, Q, V, W, X seem the trickiest. So a puzzle that I sometimes play with is, what is the simplest addition of another segment or two on a 7 segment display, that preserves the clarity, but gives an intuitive reading of letters too? Is it as on an HP41 for example?

[Steve Simpkin]

Hmmm they may be pretty old...
   

[Peter Klein]

The HP-41 series used a 14-segment display. That seems to be the minimum for display of all Latin letters and Arabic numerals. Fourteen segments can display all upper and lower case Latin letters with the exception of lower case "s." With a 7- or 9-segment display, you have to mix cases. And some letters are impossible in either case, unless you fudge a few. That "fudging" may be acceptable to people like us, but probably not to the general public.

The Wikipedia article on the 7-segment display,
https://en.wikipedia.org/wiki/Seven-segment_display
contains a chart showing how each letter and number is constructed. Under "See also" at the end of the article, there are links for the other display types with more segments.

If we don't care about which letter case we use, the seven segment display can show all numbers, including hex digits A-F. But letters K, M, V, W and X are missing. And G, S, and Z are can be confused with similar-looking numbers. 9 segments is better, but still doesn't cover everything.

14 segments is probably good enough for most purposes, but even it misses some punctuation marks like double quotes. 16 or 22 segments are better, but probably don't pass the cost-benefits analysis. I suspect that's why they weren't widely used. Once we have enough memory and processing power, it is often better to use a dot matrix display if you want to show any possible character, This decreases readability on lower resolution displays, but assures that one can show any character properly.

I find the 7-segment numeric displays of the Voyager series to be the most readable of all the HP LCD models. I also like very much the lower (numeric) half of the HP 30B (repurposed as a WP-34s). In comparison, the dot matrix numeric displays of the HP-32s, 32sii and 33s are good, but not as pleasing to my eye. The all-dot matrix display of the 42s does the job, but I don't like it so much because of its small character size and finicky contrast. The DM32 and DM42 have a high-resolution dot matrix display where where we can have highly readable alphanumeric characters.

Consider the HP 30B, which was repurposed for the WP-34s. It uses a 7-segment display for the main number display (lower part), and a dot matrix display for the upper part. I can almost hear the discussions that went on between the engineers, bean counters, usability experts and marketing types. They came up with a compromise that was good enough for a business calculator, and acceptable but not ideal for the "do absolutely everything" WP-34s. The numbers are very readable. The alpha characters are reasonably so, but we might grumble about them.

The history of calculator displays is a classic case of compromises between what needs to be displayed, current technology, cost, readability, and how much the intended audience will accept the compromises. If you have a WP-34s, type h X.FCN, scroll to WHO and XEQ it. You will see a wonderful example of exactly such a compromise, as the names display both in dot matrix and then 7-segments.

[Eric Rechlin]

(12-07-2023 11:17 PM)Peter Klein Wrote:  Fourteen segments can display all upper and lower case Latin letters with the exception of lower case "s."

There are a lot of letters that end up being quite unattractive (not just "s", but "q", "x", "y", and "z" as well, among others to lesser degrees) if you attempt to make them lowercase on a 14-segment display, but all are possible. I suspect that's why HP didn't even attempt to support lowercase on the 41 until the Halfnut, and even the Halfnut's lowercase support is well-hidden and only accessible with a special ROM module (but they did manage to make all characters distinct).

[Jeff_Birt]

(12-07-2023 11:17 PM)Peter Klein Wrote:  The history of calculator displays is a classic case of compromises between what needs to be displayed, current technology, cost, readability, and how much the intended audience will accept the compromises. If you have a WP-34s, type h X.FCN, scroll to WHO and XEQ it. You will see a wonderful example of exactly such a compromise, as the names display both in dot matrix and then 7-segments.

I like to tell students that engineering is the art of compromise. You do the best you can to meet requirements given the relationship between time, cost and quality.

[Johnh]

I reckon you can get tolerably legible alpha-numeric legibility with 12 segments. Take the basic 7 and split the middle horizontal to make 8, then add 4 diagonal elements to form an 'X'. All the letters can look ok, mainly capitals except that d and t work better as a lower-case shape.

[Garth Wilson]

(12-07-2023 11:17 PM)Peter Klein Wrote:  The Wikipedia article on the 7-segment display,
https://en.wikipedia.org/wiki/Seven-segment_display
contains a chart showing how each letter and number is constructed.

When I made my first computer almost 40 years ago, I did the "impossible" characters, for example making the M an upside-down capital U, the W an upside-down capital A, and the K an F but move the top horizontal segment to the bottom.  Some of the characters took some imagination to make out.

[Paul Dale]

I was quite chuffed once I figured out to do the M and W on the seven segment display on the WP 34S using two digits. I do agree that some other letters aren't ideal but I think we ended up with something quite readable.

The mixed display was both a boon and a curse. The processor includes an LCD driver and it's pushed to its limit handling the 20b/30b display. The display was probably the biggest limitation of the hardware, however the very limited battery backed RAM also came into play. Likewise, the slightly less limited flash and volatile RAM are also used to their limits.


Pauli

[Peter Klein]

(12-08-2023 11:12 AM)Paul Dale Wrote:  I was quite chuffed once I figured out to do the M and W on the seven segment display on the WP 34S using two digits. I do agree that some other letters aren't ideal but I think we ended up with something quite readable.

Pauli, you and the 34s team did great with what you had available. I still remember when I first saw the “WHO” screen. I thought, “What’s with the backwards J? And an instant later: “Ah… yeah!” It was a pleasure to see this on-the-surface example of the ingenuity that went into that machine. It’s like the Tardis—much more inside than you can see outside. And even the latter is impressive.

—Peter