The first system I worked on in the USAF had 512 bytes of core memory¹. But it only used 320 of them, as the system was hard-coded to 80-columns (for both punc

The first system I worked on in the USAF had 512 bytes of core memory¹. But it only used 320 of them, as the system was hard-coded to 80-columns (for both punch-card and printer). Since it was fully duplex, it had 2 send and 2 receive buffers of 80 characters each. It would flip the role of the buffers as they became full or empty. I once had to replace the core memory array when one bit went bad. By pure bad luck, it was in one of the first few columns where the end-of-message sequence was expected, and the bad ferrite meant the system got hung up waiting for an EOM that was never detected. Bad donut. No message. ;/ ¹ https://c1.staticflickr.com/1/40/109018526_8edb26b499_b.jpg https://c1.staticflickr.com/1/40/109018526_8edb26b499_b.jpg