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||| Simple OS demo for 6.004 Beta processor --     4/19/94 Steve Ward
||| os.uasm: The top-level file, which references (via .includes)
|||  files kernel.uasm, containing the OS kernel code, and user.uasm,
|||  containing the user-mode code.
|||
||| os.uasm and its .includes contain a primitive OS kernel for the Beta
|||  along with three simple user-mode processes hooked together thru
|||  a semaphore-controlled bounded buffer.
|||
||| The three processes -- and the kernel -- share an address space;
|||  each is allocated its own stack (for a total of 4 stacks), and
|||  each process has its own virtual machine state (ie, registers).
|||  The latter is stored in the kernel ProcTbl, which contains a data
|||  structure for each process.

||| The getkey() SVC used for input has a 1-char buffer; you can
|||  easily overflow the buffer by typing fast.

.include beta.uasm		| Define Beta instructions, etc.
.options clock tty

||| The file kernel.uasm contains a primitive OS kernel for the Beta.
.include kernel.uasm

||| The file user.uasm contains all of the user-mode code for our
|||  little demo.  This includes three user-mode processes, which
|||  communicate using semaphores.
.include user.uasm

||| Here's an unretouched sample of output from a BSIM run of the demo:
||| 
||| Start typing, Bunky.
|||                                                
||| 00000000> hello
||| ELLOHAY
|||