On Fri, Sep 25, 2020, 9:22 AM Noel Chiappa wrote: > > From: Warner Losh > > > I'm pretty sure PDP-10 wasn't 1's compliment / was 2's compliment.. > > Just to confirm, I pulled out my PDP-10 Hardware Reference Manual; Vol I - > CPU > (EK-10/20-HR-001), and it does indeed say (pg. 1-12): "The fixed-point > arithmetic instructions use 2's complement representations to do binary > arithmetic." Selah. > Back in school, we had our machine organization course. When we learned about 1's complement, the professor said "I've used a lot of machines that had this. You will likely never see one with it. There are no operational machines on campus with that." It stuck with me. We had a TOPS-20 machine... the odd turn of phrase was due to a professor that had a board of unknown origin hanging on the wall that was a rumored to be a CDC or similar... ah, the mid 80s... Warner >