Soda Hall Abacus
The 4th floor of Soda Hall at University of California, Berkeley, home of the computer science department, features a fully-functional six-foot wooden abacus, built by local cabinet maker Arm & Hammer Cabinet Shop in 1974. It is a Japanese abacus (soroban), with four lower beads and one upper bead on each rod. It is oriented vertically, with the ones position at the top.

This set shows the abacus in detail, and shows some simple additions and subtractions being performed on it by me, a UC Berkeley computer science graduate student, step by step.
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