𝓗.A. Abacus - JulTob/Mathematics GitHub Wiki

The Abacus is an artefact used historically to ease calculations and keep track of accounting and arithmetic.

The Basic abacus is quite simple. A horizontal grid of sticks with doughnut-shaped stones, usually with different colours. Each bar contains 10 stones (but other kinds of abaci might contain other numbers of stones with separations.

The Initial position is with all the stones on the right side (or down).

The first, or lower, line of stones is the units. By moving stones to the left side (or up) you add units. Similarly, the next line is the tens, the next one hundreds, etc.

┠────────────────────🔴🔴🔴🔴🔴🔴🔴🔴🔴🔴┨ 0
┠────────────────────🟠🟠🟠🟠🟠🟠🟠🟠🟠🟠┨ 0
┠────────────────────🟢🟢🟢🟢🟢🟢🟢🟢🟢🟢┨ 0
= 0

┠────────────────────🔴🔴🔴🔴🔴🔴🔴🔴🔴🔴┨ 0
┠────────────────────🟠🟠🟠🟠🟠🟠🟠🟠🟠🟠┨ 0
┠🟢🟢🟢🟢🟢────────────────────🟢🟢🟢🟢🟢┨ 5
= 5

┠────────────────────🔴🔴🔴🔴🔴🔴🔴🔴🔴🔴┨ 0
┠🟠🟠🟠────────────────────🟠🟠🟠🟠🟠🟠🟠┨ 3
┠────────────────────🟢🟢🟢🟢🟢🟢🟢🟢🟢🟢┨ 0
= 30

┠🔴🔴────────────────────🔴🔴🔴🔴🔴🔴🔴🔴┨ 2
┠────────────────────🟠🟠🟠🟠🟠🟠🟠🟠🟠🟠┨ 0
┠────────────────────🟢🟢🟢🟢🟢🟢🟢🟢🟢🟢┨ 0
= 200

┠🔴🔴🔴🔴────────────────────🔴🔴🔴🔴🔴🔴┨ 4
┠🟠🟠🟠🟠🟠🟠🟠🟠🟠────────────────────🟠┨ 9
┠🟢🟢🟢────────────────────🟢🟢🟢🟢🟢🟢🟢┨ 3
= 493

To add to a line you push stones to the left, and when the line is full, you move all the stones to the right, but also move one stone from the next line to the left.

This is similar to how computers add numbers, just with two stones for binary code, instead of ten for decimal as shown.