Got Slide Rules? (note: we have a slide rule trader. No longer available.)

Off Topic MakerTrade
#1

@ioport51 has been rearranging his man cave. As with any domestic archeological dig, many unusual items have surfaced. One of them is this HP calculator:

HPfront
HPfront1440Ă—932 1.15 MB

He did not know what it was. Neither did his late-night facebook following friends. So I posted it to the DMS Discord app. @themitch22 identified it as an HP-16C Computer Scientist which is/was a programmable pocket calculator that was produced by Hewlett-Packard between 1982 and 1989, and was specifically designed for use by computer programmers, to assist in debugging. Yay, Mitch!

So then he told me to ask if anybody wanted it. But then came in and said “and ask if they have a slide rule to trade”. Today, that morphed into his desire for a bamboo slide rule. And told me about his dad spending what was then a BUNCH of money on a used bamboo slide rule - and nearly being smothered in his sleep by his mom for doing so. I guess that makes it a sentimental desire. (Personally, if I were to lust after a slide rule, it would be after one of those gigantic ones like my physics teacher had for demonstrating in class. Because hell - six-foot-long oversize anything? AWESOME!)

But I digress.
Larry is interested to see if there are any slide-rule traders out there who would like this little museum-piece of a calculator. If not a slide rule, tell him whatcha got. Microprocessors?

While the model number is not imprinted on this thing anywhere, it comes with an oh-so-groovy faux leather case, suitable for any pocket protector. Or even a protector-free pocket.

HPcase
HPcase1440Ă—735 995 KB

It also has this interesting key to information printed on the back that I presume is important but is meaningless to right-brained me.

HPback
HPback1440Ă—894 1.24 MB

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#2

HP calculators are actually quite collectible. You might check eBay prices before junking it.

image
image750Ă—1334 532 KB

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#3

I have one just like it and I’ve had it for many years. They were quite the rage before we could calculate in Hex on a pc easily.

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#4

I’ve got a slide rule that my uni threw away, let me go check and see. I do some software debugging in my day job, and I’m a proud owner of 3 HP 15Cs, a HP 11c, and an HP 48G.

Edit: I laid hands on it. I have a Pickett n 3-es It’s in pretty good condition, here’s an ebay listing of one in a bit worse condition for the visual people.

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#5

fixed now… :+1:

#6

Sorry, try this one:

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#7

Jeezemplots!! I only paid about $200 for my first scientific calculator! And about $130 for the 2nd, after i left the first under a desk for a few minutes too long. And the 2nd was programmable.

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#8

Malcolm - Larry says you got a deal! He says to tell you he just found another one - that doesn’t seem to come on. May be an easy “new battery” fix or completely unfixable. Do you want both? (he was pleased that somebody he actually knew was interested.)

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#9

Beth, I remember when I was in high school taking advanced math classes, my parents got me a reconditioned Texas Instruments SR-10 calculator via a TI employee/pal. My cellphone calculator is more advanced than that thing was. Personally, I had been hoping for an SR-50, since they had functions like sine and cosine. But either way, I’m thinking that not-new SR-10 was something like $50/apiece with employee discounts included.

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#10

Thanks Mike -
The id that Mitch made last night was a sales posting somewhere. So I had a pretty good idea of the perceived value. Whether they actually sell for that remains to be seen, but…

However, while Larry and I are both proficient at buying crap on eBay, we are not so good at the sales side. I did my first listings recently (like within past six months) and was pretty awful at keeping up with the communication with buyer side of the equation. I’ll likely return to the “donate to charity and be happy it’s gone” method.

Larry mostly just tries to convince his daughter that she should be his eBay sales staff, but isn’t terribly generous with his payment split offers. So that ain’t happening.

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#11

Yeah, I’d take them both for sure. I’ll see if I can scrounge up another slide rule lol.

#12

I’ll drop them by your abode this week. I’ll text Shay to alert you guys when I do.

#13

I’ve got two of my dad’s slide rules from when he was in college in the '50s. One’s pretty cool, it’s a “pocket” model, six or eight inches long, marked “Made in Allied Occupied Japan” on the back.

I also have a HP-15C RPN calculator from taking calculus in the '80s. And I remember when the UIL had a high school slide-rule competition. Guess that makes me old. :smiley:

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#14

I remember slide rules well, because my grandpa used them often. I remember always being impressed with how smoothly the sliding part moved between the static parts. And they didn’t have RPN (whatever that is) when I was in high school. (1975 grad of LHHS). So I’m obviously older than you.

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#15

RPN = “Reverse Polish Notation,” the nickname for the HP calculator programming method. Program commands are put into a Last-In-First-Out stack. That’s about all I remember, except now I’m wondering where my HP-15C is squirreled away after two moves in 5 years.

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#16

“They” had Reverse Polish Notation as a proposal as far back as 1954, in practical use since 1960, and in everyday handhelddesktop calculators since 1968, so “They” had RPN for your high school career…
EDIT: to correct that 1968 was when RPN was employed on DESKTOP calculators; handheld didn’t happen until 1972 according to Wikipedia.

#17

Here’s my example on why RPN is amazing compared to “standard” calculators.

Say you want to evaluate the following expression:

4(3+5)

You’d type in

3
ENTER
5
+
4
x

The idea being you only ever type numbers and what you want the calculator to do, instead of parentheses. The downside is you need to work the problem in the right order, but it’s way faster and less prone to typing mistakes if you know what you’re doing.

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#18

For 4(3+5), you could also enter:
4
ENTER
3
ENTER
5
+
X

Both would get you 32 as an answer. the main advantage of RPN is that the order of operations is explicit, with no need for parentheses. The stack-based approach makes it easier for the hardware to do the computations as well - a big deal on early (read expensive) silicon.

Every ENTER pushes a number onto the last-in-first-out stack. Every operator/function pulls the requisite values (usually two for operators (like +, *, /, and -), one for functions (like 1/x, SQRT, or SIN)) off the stack, computes the operation, and pushes the result back on the stack. The number currently on the top of the stack is also shown on the screen.

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#19

I didn’t want to go into the complication of the stack lol. That’s hard to “see” in your mind without having seen how it works on a multi-line calculator like the 48G or the 35S.

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#20

image HP hat in 1980’s when they used RPN in some calculators.

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