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Paper Tape Input

Instructions: LOAD n, ADD n, SUB n, MUL n, DIV n, STORE
Accumulators hold 23-digit numbers
ACCUMULATOR: 0  |  STEP: IDLE

Harvard Mark I (IBM ASCC)

1944 — Harvard University

Designed by Howard Aiken, the Mark I was a 51-foot long, 5-ton electromechanical computer with 750,000 components. It had 72 accumulators, each storing a 23-digit decimal number, plus 60 constant registers.

Instructions were read from a 24-channel punched paper tape. A single multiplication took about 6 seconds.

"First actual case of bug being found" — In 1947, a moth was found trapped in a relay of the Mark II. Grace Hopper taped it into the log book, coining the term "debugging."