A gladiator for snaky adders? Answer: the “Addiator”

Ok, I went off track a bit on this title (a hypothetical crossword clue), but I really like the name of Arithma’s handy old mechanical Addiator. I came across this particular one at a church rummage sale.

As detailed at John Wolff's Web Museum "Addiator," originally the brand name of the German manufacturer Arithma, became the generic term for a host of similar devices used primarily for addition and subtraction. The Addiator I bought (25 cents!) came with no instructions. However, I quickly surmised that I ought to insert the stylus (clipped to its right side) into the slots next to the numbers and move them around somehow. Clearly the top set of numbers would be used for addition, and the bottom for subtraction. However, rather than puzzle it out any further, I prevailed upon my son Hank, a professional programmer, to figure out how it works. He explains:

“The trick is knowing this simple operating rule for both sections of the Addiator: Move gray numbers towards the middle of the machine, but if it becomes red, you must move it outwards and around the bend. For example, let’s say you want to calculate the following sequence of additions and subtraction: 0 + 98 + 54 – 77. Before doing anything else check the display of numbers in the middle circles. If they are not all at 0, pull up the reset bar at the top of the Addiator.

Step 1, (0 + 98), top half: Insert the stylus into the gray slot next to the 8 in the first column, push toward the middle (down). An 8 is now appears as the first digit. The display should show 08. Do the same for 9 in the second digit column. You now have 98.

Step 2, (98 + 54), top half: Insert the stylus into the red slot next to the 4 in the first column. Since it is red it gets pushed toward the top. The top is rounded, you should push the stylus around the bend and back down. This has the effect of "carrying" the one into the next digit. The display now has an up arrow for the second digit and a 2 for the first digit. Do the same with the 5 in the next column, which pushes the third digit to 1. You should now have 152.

Step 3 (152 - 77), bottom half: Insert the stylus in the red slot next to the 7 in the first column. It is red, so it gets pushed down and around the bend. The display should now read 145. Do the same with the 7 in the second column. You should end with 75.”

I tried this and it worked! Now I have no excuse for adding up my deposits incorrectly, which I do on an embarrassingly frequent basis, considering I am an engineer and all.

PS. Contrast the Addiator – based on an 1889 invention – to 2008 technology in the form of the similarly-sized (amazingly small!) Samsung Instinct demonstrated in this video by Sascha Segan, Lead Analyst for Mobile Devices with PC Magazine. This PDA phone offers a readily accessible calculator via the initial touch screen. I’ll bet it even does multiplication and division!