ADAMSATOR

About the Addiator

Before electronic calculators, pocket slide adders used numbered metal strips and a stylus. The Addiator, introduced in Germany in 1920, was a well-known example. Each strip represented a decimal place; windows above showed the total. The Adamsator works the same way using touch.

Why two colours?

The challenge with a sliding adder was carrying. When a column's total passed 9, it had to show the correct final digit and add 1 to the column on its left.

The clever solution combined coloured teeth with a hooked slot. Cream meant the number could be added directly, without carrying. Red meant a carry was needed: the slider moved the opposite way, and the stylus went around the hook to advance the next column. As the sliders moved, the colours visible beside the numbers changed too. The machine therefore showed which movement was needed, making carrying possible with a few simple strokes and no gears.

Addition

Choose Addition. Select the numbered tooth in the appropriate column and slide to the end of the track: cream down, red up. The callout bubble shows the selected number in its colour, with an arrow for the direction. On the Adamsator, going around the hook is optional; reaching the end of the straight track also completes the carry.

Entering 99,895

Start with a cleared display. In the rightmost (units) column, touch the small tooth beside 5. The bubble shows a cream 5 with a downward arrow. It is cream, so keep your finger on the screen and slide down to the end of the track, then release. The units window changes from 0 to 5.

Work right to left: select 9 in tens, 8 in hundreds, 9 in thousands and 9 in ten thousands. Each is cream, so slide down. The display now shows 99,895.

Worked example: add 213

1. Units: add 3

Select 3 in units. It is cream, so slide down. The units change from 5 to 8.

Result: 99,898

2. Tens: add 1

Select 1 in tens. It is red because 9 + 1 needs a carry, so slide up. The tens become 0 and the hundreds increase from 8 to 9.

Result: 99,908

The result digits move with your finger. If you trace around the hook, the neighbouring digit moves too. Release before completing a stroke and the digits return without changing the total.

3. Hundreds: add 2

Select 2 in hundreds. It is red, so slide up. The hundreds become 1, but the carry reaches a 9 in the thousands, producing an upward arrow.

Select 0 in thousands and slide up. Another arrow appears in ten thousands; select 0 there and slide up again.

Final result: 100,108

For each upward arrow, select 0 in that column and slide up until all carries are complete.

Clearing and Undo

Pull the silver bar upwards to clear. You do not need to clear between additions.

Undo reverses one completed action at a time, including clearing and setting a starting number. Up to 100 actions can be undone in the current session.

Subtraction

To switch to subtraction, tap the Addition/Subtraction toggle button beneath the sliders. When it shows − SUBTRACTION −, subtraction is selected. The displayed total is kept, so you can subtract directly from an addition result.

Directions reverse: cream up (no borrow), red down (borrow required). Borrowing takes 1 from the next column to the left, reversing the carrying process. For a downward arrow, select 0 in that column and slide down.

Setting a starting number

To subtract from a new number, choose Set starting number. This replaces the existing result. Enter the number using normal addition movements, then choose Done · subtract. There is no need to clear first.

The Adamsator handles non-negative whole numbers from 0–999,999. Out-of-range results are flagged; use Undo or clear.