ADAMSATOR

About slide adders

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

Addition

Choose Addition. Select each digit in its column, starting with the units. Its colour tells you which way to slide: cream down, red up. Move to the end of the track.

Worked example: 99,895 + 213

1. Units: no carry

Starting with 99,895, select 3 in the units column. It is cream, so slide down. The units change from 5 to 8.

Result: 99,898

2. Tens: a carry

Select 1 in the tens column. It is red because 9 + 1 requires a carry. Slide up: the tens become 0 and the hundreds increase from 8 to 9.

Result: 99,908

On a mechanical Addiator, a red movement goes in the opposite direction to wrap the digit back below 10. The hook lets the stylus engage the next slider and carry 1 into it. On the Adamsator, you may follow the hook or simply slide to the far end; either completes the carry.

3. Hundreds: multiple carries

Select 2 in the hundreds column. It is red, so slide up. The hundreds become 1 and carry into the thousands. But the thousands already show 9, so an upward arrow appears.

Select 0 in the thousands column and slide up. Another arrow appears in the ten thousands. Select 0 there and slide up again.

Final result: 100,108

Whenever an upward arrow appears, select 0 in that column and slide up. Repeat until all arrows have gone.

Clearing and Undo

Pull the silver bar upwards to clear the display. There is no need to clear between additions: each new number adds to the existing total.

Undo reverses one completed action at a time, including clearing and starting-number entry. You can undo at least five actions, up to 100 in the current session.

Subtraction

Choose Subtraction. The existing displayed total is kept, so you can subtract directly from the result of an addition.

Subtraction reverses the movements: cream up, red down. A red tooth means subtracting that digit requires borrowing from the column to the left. Just as addition carries 1 into the next column, subtraction borrows 1 ten from it; the opposite arithmetic requires the opposite sliding directions.

If a downward arrow appears, select 0 in that column and slide down. Repeat until the arrows disappear.

Setting a starting number

To subtract from a new number instead, select Set starting number. The previous result is replaced, not added to. Enter your new starting number with the sliders using the usual addition directions, then select Done · subtract. You do not need to clear first.

The Adamsator handles non-negative whole-number results from 0–999,999. A result outside this range is flagged; use Undo or clear.