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IBM 1401. One of the weirdest ISAs I've ever read about, with basically human readable machine code thanks to BCD.
by Joker_vD 2y ago
IBM 1401. One of the weirdest ISAs I've ever read about, with basically human readable machine code thanks to BCD.
- jonjacky 2y agoYes, it had a variable word length - a number was a string of decimal digits of any length, with a terminator at the end, kind of like a C character string. Machine code including instructions and data was all printable characters, so you could punch an executable program right onto a card, no translation needed. You could put a card in the reader, press a button, and the card image would be read into memory and executed, no OS needed. Some useful utilities -- list a card deck on the printer, copy a card deck to tape -- fit on a single card. https://en.wikipedia.org/wiki/IBM_1401 https://en.wikipedia.org/wiki/IBM_1401