Anton Aylward wrote:
Back when, UNIX started something radically different that we now consider the norm. Back when, processes were deemed expensive to create so they weren't. The CLI just ran one program at a time, had not control flow. There was a "Transient Program Area" and the CLI caused the executive to overlay the CLI with the application. Great for what were single process systems like CPM/DOS and their mainframe predecessors. When the application terminated the system somehow reloaded the CLI and you were off again.
What made UNIX radical was that the CLI, the shell, stuck around; process creation was cheap an easy and so the application was run in a sub-process. That meant the CLI could do things that weren't possible before. It could run a sequence of programs; it could run two (or more) child processes that were connected via pipe.
We take this for granted now, but back in the 70s and 80s this was radical.
Hmm, UNIX was first named UNICS, named after MULTICS, from which it took many features, including multiprocessing. As well as MULTICS, the Burroughs MCP had parallel execution of tasks, as did ICL's GEORGE 3. They all had job control languages too, and all in the 1960s before Unix was conceived. The history of computing contains a lot of reinventions of the wheel, as new people join the party or new types of hardware are built. Virtual memory and filestores are another area where it feels like groundhog day. -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org