Z:gnu-www-ja-google-engineering-talk--8dc73f-I had decided to make the syst/en

I had decided to make the system UNIX-like so that it would be portable. The operating system that we had used for many years at the Artificial Intelligence Lab was the Incompatible Timesharing System, or ITS. It had been written in assembler language for the PDP-10, so when Digital discontinued the PDP-10, our many years of work turned into dust and blew away. I didn't want to write another system and have the same thing happen, so I decided this system had better be portable. But there was only one successful portable operating system I knew of, and that was UNIX. So I decided to follow the design of UNIX, figuring that way I'd have a good chance of succeeding in making a system that was useful and portable. And then I decided to make the system upward-compatible with the interfaces of UNIX, and the reason for this was so that users could switch to it without an incompatible change.