Variable Word length CPU

... That should have said "in each byte (6 bits)..." Since the decimal digits only took 4 bits and the word mark was a 7th bit there were two bits to carry the sign. This machine was actually designed to be an off-line card reader/ punch/ print processor using tapes to offload the biger 7094 type machines. So it was very card oriented. The other two bits represented the "zone" punches off the card. I can't remember which combination(s) was considered a negative number, but it was the same for any machine reading cards. The instruction to read a card was "R" and it read into a fixed location (0, IIRC). The instructions were also variable length, varying from 1 to 8 bytes long. An instruction could leave off the addresses (indicated by a word mark on the next byte) and the addresses would be inferred to continue from the previous instruction. The 1401 machine had 16KB MAX. memory, so saving a 3 byte address was a big deal. Gil