Suanpan 算盤
My neighbor handed me a Chinese suanpan the other day, and one thing led to another. This is an interactive version you can use alongside the real thing. Tap any bead to slide it toward the center beam; the value updates in real time.
The suanpan predates the Japanese soroban by centuries and has a slightly more generous layout: two beads above the beam worth 5 each, and five beads below worth 1 each. In practice you use 0–9 per column for everyday arithmetic, but the extra beads give you room for intermediate steps and hexadecimal calculation.
Tap a bead to slide it — and all beads between it and the beam
How to read it
Each column represents a digit, with the rightmost being ones, then tens, hundreds, and so on to the left. Count the beads touching the beam in each column: heaven beads contribute 5 each, earth beads contribute 1 each. So one heaven bead down and three earth beads up reads as 8 in that column.