I have a question about this ultra simple calculator and was hoping that someone might enlighten me. (Apologies for being just a bit off topic.)

In the manual, in the section on the calculator's "Operations", it begins like this:

----------Quote----------

Before calculation

* To obtain an accurate result, be sure to perform the following operation before starting calculation.

Power switch "ON" -> 0

1.1111111 x= -> 1.2345678

----------End Quote-------------

I am very curious as to why they recommend that one performs that multiply. What could the consequences of not performing it be?

Maybe they think it's a way for you to tell whether the batteries are too low for it to do calculations properly?

It's obviously an easy calculation to enter, though it doesn't really test things very thoroughly because there is no carry when adding the partial products.

That makes sense. I kept thinking that it might have to do with resetting/initializing the state of the calculator somehow, but that did not make sense right after a power-on. It did not occur to me that it might just be a test.

Although, if it is meant to be a test, I am a little surprised that they didn't put some statement in the manual as to what to do if one sees the wrong result...

While I do not know anything about the accuracy of this calculator, I wonder why 1,1111111 squared should return 1,2345678. The true result is 1,23456787654321 which rounds to 1,234567**9** on an eight-digit machine.

Dieter

Tested on a few vintage calculators:

On the Sharp EL-811 and on the Sharp EL-814:

1.1111111 [x] [+=] gives 1.234567**8**

Same on the Rockwell 63R, however on the Sharp EL-5803 it gives: 1.234567**9**

Hurl it at the nearest wall?

Possibly the engineers weren't confident in the power-on reset, and expected that if you did a simple calculation like that and didn't get the right answer, that you would turn it off then on again. [insert "IT Crowd" reference here].

I assume that to correctly calculate the last digit, the calculator must internally have one more digit of precision than it displays.

I had never heard of the EL-5803 before. It seems like an odd calculator from the very little info I can find on on the web. This is the only picture I could find: http://tinyurl.com/a7udsx3

Well, it seems like you have a rarity. Do you know if it was built for some specific audience? Or how many were made?

Interesting, it has (shifted) functions for frequency (Hz) and decibels (dB).

I don't know how many were made. I think that the targeted audience was electrical engineers: it was build to simplify calculations of impedance, decibels and angular frequency. It has also dedicated keys for units: pico, nano, micro, milli, kilo, Mega and Giga, and can do operations on complex numbers using the keys [R.P] and [I.P] (real part & imaginary part).

It's from 1977. It's listed in this article: Popular Science June 1977: Specialized Calculators shortcut tough problems

*Edited: 13 Feb 2013, 12:34 a.m. *