Numbers and accuracy

[rrich]

A kid had just entered University as a freshman and was wandering about campus. He noticed a lot of the upperclassmen carrying a sheath on their belts. The kid thinking it was a weapon and thought that he might need one on the campus. He cautiously approached one of the upperclassmen and inquired about the 'weapon'.

The upperclassman explained that it wasn't a weapon but a slide rule. (A battery less calculator for all of you youngsters.) The upperclassman says that he can not multiply or divide without the slide rule and goes on to demonstrate and explain how it is used.

"For example two times two. You put this index or one over the two and then read the number below this two. Anyone can see that two times two is three point nine eight."

If any of you are rushing out to acquire a slide rule, beware that dividing zero by infinity can have disastrous results. :) :no:

[AlexS]

beware that dividing zero by infinity can have disastrous results.
But dividing anything by zero on an electro-mechanical calculator can really set it running...until the motor burns out. DAMHIKT.:D

[AlexS]

The slide rule is very accurate...but not very precise.

[rrich]

But dividing anything by zero on an electro-mechanical calculator can really set it running...until the motor burns out. DAMHIKT.:D

Ah yes, the joys of a Frieden, Marchant, Monroe.

And today I can buy a solar powered calculator with fractions, trig functions, roots and powers all for about $11.

I was working for GE in their Process Control department. The subroutine to do square roots was 50 or 60 instructions long. I rewrote the routine using the technique that we used on the Frieden in about 15 instructions. It was shorter and ran faster. No body believed it would work but they couldn't understand why they were getting the correct answer.

GE/PAC Forever

[AlexS]

We had Marchants & Monroes. Once, one developed a mechanical squeak, so someone (no names, no pack drill) sprayed some WD40 into it while it was running.

Let's just say it got rid of the squeak.

The thing was, with those old machines, you quickly learned the best way to do things, or you wasted a lot of time. Then when the first computers came along, you learned the trade-offs between memory and computation time.

[BobL]

The way I was taught to use a slide rule on large numbers of inputs was to first change all the inputs to powers of 10 and perform an order of magnitude calc so you knew what that was. Then do the slide rule calc and compound the result with the order of magnitude. Then at least you would usually be within an order or magnitude. It's more work but results in a far more reliable answer.

Once calculators came in folks began blindly punching numbers in and mistake multiplied. The calculators I like using are those that use stacks and reverse polish operations, like the 1980's type Hewlett Packards. We had a desktop model at work that had a one line LED display and could store/recall up to 10 inputs so you could go back and check if the entered inputs were OK.

I still have my HP 41CV and it still works on mains (battery is long gone). For a few $ you can buy a 41CV emulator App for mobiles so I have it with me wherever I go. Its my go to calc in the shed. Still have my slide rules too - I'll bring them out when the grandson gets old enough.

[Fuzzie]

1+ for reverse polish. I still occasionally use a command line one I original wrote in Fortran as well as a CharityWare (http://www.menees.com/)windows 95 applet I picked up around 1998 that still runs fine on Win10.

[damian]

You can take all that for a long walk off a short pier.

Many years ago I was running a new lab and I knew the work would get semi routine.I had the choice of writing a program to reduce my data or setting up a spreadsheet. I did the latter ad have never looked back. Now I use them for everything. All you inputs are laid out clear and day and labeled. All your equations are visible traceable and editable.

I did one just this morning laying out my budget for the next few months.... quick as lightening easy as pie clear as daylight :D

Best thing since sliced inverse polish...

[BobL]

You can take all that for a long walk off a short pier.

Many years ago I was running a new lab and I knew the work would get semi routine.I had the choice of writing a program to reduce my data or setting up a spreadsheet. I did the latter ad have never looked back. Now I use them for everything. All you inputs are laid out clear and day and labeled. All your equations are visible traceable and editable.

I did one just this morning laying out my budget for the next few months.... quick as lightening easy as pie clear as daylight :D

Best thing since sliced inverse polish...

It depends on the sort/amount of data or problem you want to solve.
If it's data sets or repetitive work then spread sheets are the go and I use them a lot for motor HP calcs, and airflow and dust particle calcs, but for calculating one off short function/equation in the shed I can have an answer with my reverse polish calculator emulator on my mobile far faster than it takes for me to go back up to the house and load up a spreadsheet on my computer.

[Mr Brush]

I was lucky enough to go through my education in the UK just as a lot of changes came through. Started with a slide rule for the first few years, progressed to a basic 4 function calculator in lower school, and by the time I was going through uni had moved up to an HP32S Scientific with RPN (couldn't afford the HP41C in those days). Amazingly, the HP32S is still going strong some 35 years later; it only seems to need a new set of batteries every 10 years or so !

With the advent of mobile phone apps I was finally able to get that HP41C - there is a very good free app (search for "go41c" in the Play Store).

[AlexS]

Slide rules! When I were a boy, we couldn't afford slide rules, had to make do with 7 figure & 13 figure logs for spherical trig calcs.:)

The HP41c was a wonderful piece of technology, especially with the peripherals that could be attached and the ability to scan in programs from a bar code. I once wrote a HP Basic program for the HP9845 where you could type in a HP41C program and plot it out as a bar code program.

[Mr Brush]

I forget what the little modules were that plugged into ports in the top of the 41C? Pre-written program packages for different applications? I do remember the bar code scanner option.

Weird that I still find it easier to use an RPN calculator after all these years. You just get used to thinking that way.....

[rrich]

So, does 2 x 2 equal 3.98, 3.99, 4.0 or 4.1? :)

BTW - Thank you, Damian for "You can take all that for a long walk off a short pier.". It brings back memories of the 'Old Man'.

[Mr Brush]

I think you'll find that the correct answer is "A Suffusion of Yellow".....clearly the number 4 has all sorts of properties we don't yet understand. For fans of Douglas Adams: -

https://www.urbandictionary.com/define.php?term=A%20Suffusion%20of%20Yellow

:D

[BobL]

I forget what the little modules were that plugged into ports in the top of the 41C? Pre-written program packages for different applications? I do remember the bar code scanner option. can’t remember either. Mine had a magnetic memory card reader/writer. I wrote a 200 line, 12 card nuclear reactor program for it. That took 20 minutes to run.


that I still find it easier to use an RPN calculator after all these years. You just get used to thinking that way.....

Me too.

[Chesand]

I obviously pre-date all of you as never touched a slide rule. Had to learn all the tables up to 20 times and used logarithms.

[damian]

It depends on the sort/amount of data or problem you want to solve.
If it's data sets or repetitive work then spread sheets are the go and I use them a lot for motor HP calcs, and airflow and dust particle calcs, but for calculating one off short function/equation in the shed I can have an answer with my reverse polish calculator emulator on my mobile far faster than it takes for me to go back up to the house and load up a spreadsheet on my computer.

You do calculations in your shed? Ah therein lays the problem :D

Actually if I'm on the computer I find myself doing even the simplest calculations on a spreadsheet now. Possibly because if I use a calculator by the time I start a second calculation I've already forgotten the first one I did... and I do mean START the second.... Sometimes I think I need to write myself a note before I getup so I can remember why I entered the next room.

Mention of "apps". My HTC came with a thing called tasks. It's a series of to do lists. The most handy thing I've had in ages. Obviously shopping lists, I've also built a check list for traveling and one for camping, boating. All sorts of lists. I can almost remember things now...