I’m no engineer :) but for your date problem can you use the end/maturity date converted to a Julian date and work backwards?

you COULD pgm the Excel sheet to act dynamically exactly like the stack does...

That’s what I’ve done. However, right now, for each function I enter, I have to enter the corresponding Excel formulas. E.g. if the DM42 function is “X>0?” then in Excel I have to type the appropriate “IF(....)” formula and in effect tell the spreadsheet what the stack should do. Which is nice as it forces me to think about what the stack does.

What would really be cool is if I could get the sheet to recognize the DM42 function and automatically insert the corresponding formulas. I don’t think that is possible. And anyway it occurs to me that I’d be basically retreating to the familiar instead of forcing myself to learn the new.

Wow, this thread fascinates me (and makes my head hurt!). I haven't picked up my HP12C in YEARS...I wouldn't even know where to begin without Bloomberg, Intex and Excel!

by "act dynamically" I meant an animation

if you did that I wanna see it!

Oh, that would need VB - I mean the goal is to program the calc, not to get sucked into programming VB/Excel ...

Right? I mean, the sensible thing is to type in the CUSIP and read everything off the screen ... but that’s no fun. And suppose you’re stranded on a desert island and need to evaluate a bond?

Back in the day that's exactly what I used my 42s for as a young engineer - I could take that with me out to the shop floor to troubleshoot and tune equipment / machinery (with programs I had written) on the fly without having to go back to my desk all the time. It was awesome.

I didn’t know enough about the calendars to understand what you meant at first, but I now see that is how HP did date calculations. https://archived.hpcalc.org/hp42s/programs/date/olddate.html?fbclid=IwAR176kIGajlg6ahd7Ar8OGFsOOwE vv8sIRxtaXpKKQE9udQxpyMgu80lpZs

The DM42 has DATE+ and DDAY built in, fortunately.

I’m trying to do something different, basically if I have Oct 16, 2020 and add 4 months I want to get Feb 16, 2021. And I have that working fine. My remaining issue is that if I have Oct 31, 2020 and add 4 months I don’t want Feb 31, 2021, I want Feb 28, 2021 unless 2021 were a leap year in which case I’d want Feb 29, 2021.

I think I found out how to do it. I just use DATE+ to add 0 days to the date, if the date is Feb 31, 2021 the function will return an error, there is a flag 25 that tells the calculator to ignore an operation that results in an error, so that’s sort of a test I can use.

Never was an HP 42CV. There were the 41 series that included the 41C, 41CV and 41CX. Each was an upgrade over the other. THE calculator of choice for Engineers and Surveyors. British Airways and Air France always had a 41 onboard the Concord, and every space shuttle mission ever flown used a 41 as well. I've got a box of 12 or 20 of them in a closet. Along with many of the "modules" that were used with them, including the "Financial" module. More than 20 years ago I came up with a repair to the magnetic card readers that would fit the 41 series; the drive wheels would get gummy with age and not pull the card through. It was a simple fix IF you had the right materials, that cost me less than a dime. So I joined the forum at www.hpmuseum.org and for the cost and time of sending ME a picture postcard from your part of the world, I would send YOU the materials and instructions to fix your card reader. I got postcards from around the world and I've still got the stunning scenic photo book of Blue Sardinia that Luigi sent me.

https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=57

Nowadays, I use an HP41C app on my smartphone. :rolleyes:

Haha, good points! I actually love building things in Excel/VB for fun, but the calc programming is over my head. Super cool that you are doing it, great thread.

Honestly, it is over my head too. I’ve gotten slower and stupider with age, plus I’m so much busier than I was as a teen, trying to do this in 10 minute snatches between paying work and honey-dos and volunteer work. I miss being young, mentally agile, and a whole summer of nothing to do but futz with stuff.

I have a HP41?? somewhere. Going to find it and see if it still works.

Yes, 41 !
The gold standard.

So - does anyone still use a physical calculator in their work? Or is this just a hobby and collector thing now?

Way back in the 80's during my early years at land surveying, the HP41 was the ticket as HP had developed a "Surveying" ROM that in it's module form would plug in to the back of the calculator. Did all kinds of Surveying routines. Even made the one old fellow I knew retire his palm sized Curta mechanical calculator. Now if you want to see a really cool mechanical device, go check one of those out. Highly collectible back then I imagine even more so nowadays.

So anyway, I got pretty good at programming simple routines for the 41 that the ROM wouldn't do, and other times, well......

The crew loaded up in the old suburban one morning and we had about an hour travel time to the job at the new industrial park. We were to meet with an Engineer on what he needed us to layout. The morning joint had already been passed around going down the road and I didn't partake. But I did grab Joe the Party Chief's HP 41 while he was driving.

Now the 41CX had a built in clock. That and more memory set it aside and above the 41 C and CV variants. A clock meant you could (of many things) set an alarm. So I calculated our travel time and what time we would probably meet the engineer on site....and went to work programming.

I'm looking at my watch. It's coming up on 8:30 a.m. and Joe has a really good buzz on. He's got his calc on the hood of the suburban and talking to the Engineer making a few calculations, and while in the middle of making some calcs I see my watch hit 8:30. Bingo. Party time. Joe's HP 41CX starts beeping incessantly and uncontrollably with the text

EAT AT JOES

scrolling across the screen. He's flipping out. I'm hiding behind the suburban about doubled over laughing. It goes on for about 30 seconds and he has her back under control.

30+ years later, Joe is still my friend and we occasionally laugh over that story.:D:D

Just for fun several years ago.



http://forums.pelicanparts.com/uploa...1602662882.JPG

Where is the "CRAY" module?

NVTS 2.4 Module.

Seriously, it was all in fun with a Surveying forum since we all relied on the old 41's for so many years. Enjoy your new calc.

I just ordered the hpmuseum’s full USB stick of goodies!

Let us know how it is!

http://forums.pelicanparts.com/uploa...1602959991.jpg

I went looking for my HP41CX and found it along with some books. None of this has seen the light of day in many many years. The books are long out of print. I should scan them and then sell the physical books to collectors.

The batteries are dead. Need to fix that.

I compared the keyfeel. The HP key travel is longer and smoother, and the tactile click is "softer". The DM key has a crisper tactile click and a shorter travel, and also a more audible "click". It also may require slightly more force, at least in its brand new state. After doing the comparison, I no longer feel the DM keyfeel to be inferior to the HP keyfeel. It's just different. One is a GT 928, the other is a track 911. I do think the HP keys are more attractive, with their trapezoidal shape and multi color printing. That is pretty clear.

Hopefully the gold battery contacts in your 41 survived the old N cell batteries. Those were the one thing I really miss not having a Radio Shack anymore.

Gold ?
Whoa, gotta dig mine out to check it out.

The batteries didn't leak, contacts look good. Whew! Any rec for replacement batteries?

I have some Energizer E90 alkaline batteries for my 41CX - seems to work OK.

I do take the batteries out if letting it sit for a while.

Your description of the key differences between the DM42 and the 41CX is pretty spot on to how I would characterize the differences between the HP 42s and the 41CX. Maybe the DM42 replicates the 42s keys best they could. You may have just talked me into buying one...

They also have a DM41 that is supposed to be to the HP41C/CV/CX as the DM42 is to the HP42S.

I looked at the DM41 and it's a cool piece of hardware. I'm "backward" though and started with a 42s and so will be chasing that instead. I got the 41CX as a "I'm cleaning out the garage and don't know what this is anymore" gift from my neighbor years ago. I remember trying them both years ago when "comparison shopping" and the 42s made more sense to me.

Side note - I've got a bunch of slide rules and antique drafting instruments around too - was thinking about starting a thread on that but am guessing that will have near-zero appeal to anybody but us math/engineering geeks. Maybe somebody would bring out photos of their old Curta... (one piece of mechanical elegance I've yet to see in person...).

I've got an old Pickett slide rule a lot like the pic below that my dad brought home from work for me when I was ~13-14. They were anachronistic by then. I also have several old Japanese abaci.

I'd love a round slide rule. I need to spring for one some day.

https://ralphlosey.files.wordpress.c...slide-rule.jpg

If you start a thread, they will come.

I gave my son my old K&E slide rule, he actually uses it, a little. He's fascinated by it - log math is pretty darn cool.

He's a second year architecture student. I'm trying to push him to get a business degree or at least a business minor, take all the real estate development and management classes available, intern for a developer, telling him he'll be a better architect if he understands how the business side works. He's generally agreed to that, is taking economics classes to start out. Naturally I've given him one of my HP12Cs.

His structures class assignment last week was to build a bridge from wood coffee stirrer sticks (the disposable ones that you buy from restaurant supply stores), then the professor took all the students' bridges and tested them to failure by placing on a jig then loading with a bucket into which he poured sand until the structure collapsed. My son really took it seriously, came home to use our basement art studio, stayed up all night, glue-laminated sticks into cross beams and built a well-braced structure, left at 4 am to drive back to Eugene with his wood stick "bridge". The professor was not able to collapse it, despite adding a second and then a third bucket of sand. The video of the testing is funny. Prof is hunting for more buckets and more sand, finally gives up and calls it a pass!

I had a circular slide rule in high school, loved it.

Start the thread! What do you have to lose beside your $ as you start buying archaic computing machines?

Hell I spent $600 buying Monroe Bond Calculators on eBay until I finally got control of myself.

OK - Thread started:

http://forums.pelicanparts.com/off-topic-discussions/1076054-old-engineering-mathmatics-stuff.html#post11069395

I don't need to spend more money - I already have a collection of this stuff (gathered over the last 35 years or so)...