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May 13

Punch card loopback

Did any of the punch-card-based computers have a mechanism to move cards from the output deck to an input deck? Was this used for array indexing before indirect addressing was implemented? Did the cards contain the addresses or the data? Neon Merlin 20:59, 13 May 2024 (UTC)[reply]

I don't believe so. However there were quite a number of places which had all their data on cards and used various arrangements of card sorters, adders, multipliers and suchlike for their computing needs. See Unit record equipment. I think loading and storing via a register were implemented fairly early on. However there were commercial machines where they for instance wrote the return address into a location where a subroutine would jump to it at the end before jumping to the subroutine. Recursive routines and stacks came later! NadVolum (talk) 21:42, 13 May 2024 (UTC)[reply]

It is not clear what it means for a computer to be "punch-card-based". With very few exceptions, all mainframe computers could use punched cards for I/O until in the eighties. The readers and punches were usually separate peripheral devices but some models, such as the IBM 1442, were a combination. Each card that was read ended up in one of its two output stackers. --Lambiam 17:08, 15 May 2024 (UTC)[reply]