NOTES

Next:

- Nothing.

Optional:

- Make ReadKey block if there's no key.
    - Would have to shut off VM and start it again when there's a key.
    - How to get key to ReadKey function?
    - Function would have to be able to tell Machine that it's interrupted, when call
        to function (in CSP handler in Machine), you'd have to check the state, not
        push result on stack, and stop immediately. Later when a key is available
        you'd have to restart the CSP operation. That's probably easiest. But the
        stack got popped off for arguments. Could save all that. Or could just push
        resulting key on stack and continue. Maybe function would pass to ctl
        a function to call when it's ready to resume, and it would return the
        right value.
- Add a way to show/hide debug info from web page.
- Implement a real heap, with a free list.

Notes:

- To disable caching in Chrome, open devtools, click gear in lower-right, set checkbox.
- Design of p-machine:
    - http://cs2.uco.edu/~trt/cs4173/pspec.pdf
    - Instruction: (8 opcode, 8 op1, 16 op2).
    - 32k instructions in istore.
    - data store: elements of 8 bytes each. That's the largest size of any data type.
        - Heap grows down from the top.
        - Stack grows up from the bottom.
    - Registers:
        - PC (32-bits) points to instruction being executed.
        - SP (32-bits) points to top of stack.
        - NP (32-bits) points to bottom of heap.
        - MP (32-bits) points to bottom of frame:
            - Return value (rv).
            - Static link (sl) - link to frame of enclosing procedure.
            - Dynamic link (dl) - link to calling frame.
            - Old extreme pointer (ep)
            - Return address (ra)
            - Parameters
            - Locals
            - Computation
        - EP (32-bits) location of highest stack for frame.
            - Not sure why we need this.
            - Ah, it's to less frequently check collision with new pointer. Can skip this.
- Design of bytecode object:
    - istore: array of bytecodes (doubles).
    - Debug information.
- Design of p-machine:
    - istore: array of bytecodes, just use bytecode object.
    - data store: array of 8-byte values (doubles?).
        - Stack grows up.
        - Don't worry about heap, can probably use JavaScript heap.
    - Registers.
    - Nothing stored in JavaScript stack. All stored in object so we can restart anytime.