dumb stack machine

16-bit words
8 registers of any size
two stacks, one is active at a time

0000                - nop      - do nothing
0001                - add      - pop two numbers, push their sum
0010                - sub      - pop two numbers, push their difference
0011                - pop      - pop a number, and do nothing
0100                - dup      - pop a number, push it twice
0101                - swap     - pop two numbers, push them in the opposite order
0110                - ld       - pop an address and a value, then store the value to that address
0111                - st       - pop an address, and then push the contents of that address
1000 nnnn           - ld #num  - push 4-bit sign extended integer
1001 0nnn           - ld reg   - push contents of register n
1001 1nnn           - st reg   - pop, store to register n
1010 0nnn           - add reg  - pop, add register n's contents, push new value
1010 1nnn           - sub reg  - pop, subtract register n's contents, push new value
1011 0000           - mul      - pop two numbers, push their product
1011 0001           - div      - pop two numbers, push their quotient
1011 0010           - mod      - pop two numbers, push their remainder
1011 0011           - and      - pop two numbers, push their bitwise AND
1011 0100           - or       - pop two numbers, push their bitwise OR
1011 0101           - xor      - pop two numbers, push their bitwise XOR
1011 0110           - lsr      - pop a number, push number>>1
1011 0111           - asr      - pop a number, push number>>1 with top bit the same
1011 1000           - call     - pop a number, jump to that location, push the old program counter to other stack
1011 1001           - return   - pop a number from the other stack, and jump to it
1011 1010           - neg      - pop a number, push -number
1011 1011           - cpl      - pop a number, push ~number
1011 1100           - inc      - pop a number, push number+1
1011 1101           - dec      - pop a number, push number-1
1011 1110           - if       - pop a number, pop an address. call address if number is nonzero
1011 1111           - ifelse   - pop a number, pop two addresses, pop a number. call address if number is nonzero
1100 0000           - loop     - pop two addresses. call the first address, if it produces a nonzero number call the second one, repeat
1100 0001           - eq?      - pop two numbers, push -1 if ==, 0 if not
1100 0010           - ne?      - pop two numbers, push -1 if !=, 0 if not
1100 0011           - gt?      - pop two numbers, push -1 if >, 0 if not
1100 0100           - lt?      - pop two numbers, push -1 if <, 0 if not
1100 0101           - le?      - pop two numbers, push -1 if >=, 0 if not
1100 0110           - ge?      - pop two numbers, push -1 if <=, 0 if not
1100 0111 0000      - pick     - pops a number, pushes the number from N items down
1100 0111 0001      - pickout  - pops a number, pushes the number from N items down and removes it from the stack
1100 0111 0010      - rotate   - rotates the top three stack items
1100 0111 0011      - altstack - use the other stack from now on
1100 0111 0100      -          -
1100 0111 0101      -          -
1100 0111 0110      -          -
1100 0111 0111      -          -
1100 0111 1000      -          -
1100 0111 1001      -          -
1100 0111 1010      -          -
1100 0111 1011      -          -
1100 0111 1100      -          -
1100 0111 1101      -          -
1100 0111 1110      -          -
1100 0111 1111      -          -
1100 1nnn nnnn nnnn -(see note)- pushes address of next opcode, jumps n bytes ahead (up to 2048)
1101 0nnn           - ld *reg  - push the word pointed to by register
1101 1nnn           - st *reg  - pop a word, and store it in the memory location pointed to by register
1110 0nnn           - inc reg  - increment register
1110 1nnn           - dec reg  - decrement register
1111 nnnn nnnn nnnn - ld #num  - push a full sized word

1100 1nnn nnnn nnnn is specified with a [ starting the area to be skipped over, and a ] ending it



loop from 0 to 10:
  ld #0
  [
    dup
    ld #10
    ne?
  ]
  [
    inc
    dup
    ld #PrintDecimal
    call
  ]
  loop