On Tue, Sep 29, 2026 at 03:18:43PM -0400, Paul Koning via cctalk wrote: > ENIAC was 40 bits I think.
To a first approximation... :) Each accumulator operated on a number stored as 10 decimal digits (each in a ring counter) plus a sign. In pure binary, this would be equivalent to a little over 34 bits. Data read from cards was staged in relays before being transmitted to accumulators. There each digit was stored on 4 relays (but not in BCD). So for a 10-digit number taken from the cards, there were 41 relays (40 for the digits and 1 for the sign) storing it. (Card data could also be treated as 5-digit numbers.) Around '52 or '53, they added a core memory unit. I haven't dug into it as much as the rest of the machine, but I'm pretty sure numbers were stored in it in essentially the same format as the relays holding card data. So while calculation and transmission didn't take place in that format, there were places where numbers were represented with 41 bits. BLS
