UniFLEX

UniFLEX was a Unix-like operating system Technical Systems Consultants built for the Motorola 6809 family, supporting multitasking and multiprocessing on machines from makers including SWTPC, Gimix and Goupil that had DMA-capable 8-inch floppy drives and extended addressing for up to 768 kilobytes of RAM. Because the 6809's 64 kilobyte address space left only about 56 kilobytes for the kernel and processes combined, the whole system was written in assembly language and some Unix features, such as file group permissions, had to be left out. UniFLEX closely resembled Unix Version 7, though with command names changed to stay compatible with its single-user sibling system FLEX, used process-level swapping to disk for memory management, and could support several asynchronous terminals even on machines with less than a megabyte of RAM. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/