OS build for csc159 at CSUS
This reflects a change in professor midway through the semester
phase 0 -- phase designed to get students oriented with build environment
phase1 -- implemented the basic OS structures and components (kernel / userpace, PCB, process queues, trapframe, clock syscall, etc.)
phase2 -- implemented a basic lower half keyboard driver and allowed i/o operations via read/write syscalls
phase3 -- implemented process creation via fork syscall
phase1 -- similar to phase 1 in first part
phase2 -- implemented IPC via semaphores and message passing