Another part of computing history that seems almost completely
forgotten is ledger card systems, which is what many small offices
(if they weren't doing things manually) were using before PCs
came along and for quite a few years afterwards.
With magnetic stripes on the back of the cards, paper tape I/O
and/or high speed digital cassette drives, automatic feeder/stackers,
(relatively) high-speed card readers, and datacomm capabilities,
they were certainly true computers by any criterion.
I recall one of my Burroughs L installations which would have 4
cassette drives randomly zipping back and forth (much quieter than
your tape drives, actually quite pleasant to listen to) and an auto-reader
going through a deck of ledger cards, while another set of cards was
being fed into the printing console, stripe read and updated, printed
(along with 2 reports being printed simultaneously on the same
independent-dual-carriage 255x10cpi 2-colour dot-matrix printer),
and stacked in the back, all without any operator intervention;
fun to watch.
I'll have to dig around & see if I can find the core memory card from an
E series machine that I used to have lying around somewhere...
m