Started working on a spec, still needs a lot of work

spec.org

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+#+title: VM Specification
+#+author: Aryadev Chavali
+#+description: A specification of instructions for the virtual machine
+#+date: 2023-11-02
+
+* Data types
+There are 3 main data types of the virtual machine.  They are all
+unsigned.  There exist signed versions of these data types, though
+there is no difference in terms of bytecode between them.  For an
+unsigned type <T> the signed version is simply S_<T>.
+|-------+------|
+| Name  | Bits |
+|-------+------|
+| Byte  |    8 |
+| HWord |   32 |
+| Word  |   64 |
+|-------+------|
+* Instructions
+An instruction for the virtual machine is composed of an *opcode* and,
+potentially, an *operand*.  An /opcode/ represents the behaviour of
+the instruction i.e. what _is_ the instruction.  The /operand/ is a
+datum of one of the /data types/ described previously.
+
+Some instructions do have /operands/ while others do not.  The former
+type of instructions are called *UNIT* instructions while the latter
+type are called *MULTI* instructions[fn:1].
+
+All /opcodes/ (with very few exceptions[fn:2]) have two components:
+the *root* and the *type specifier*.  The /root/ represents the
+general behaviour of the instruction: ~PUSH~, ~POP~, ~MOV~, etc.  The
+/type specifier/ specifies what /data type/ it manipulates.  A
+complete opcode will be a combination of these two e.g. ~PUSH_BYTE~,
+~POP_WORD~, etc.  Some /opcodes/ may have more /type specifiers/ than
+others.
+* Bytecode format
+Bytecode files are byte sequence which encode instructions for the
+virtual machine.  Any instruction (even with an operand) has one and
+only one byte sequence associated with it.
+* Footnotes
+[fn:2] ~NOOP~, ~HALT~, ~MDELETE~, ~MSIZE~, ~JUMP_*~
+[fn:1] /UNIT/ refers to the fact that the internal representation of
+these instructions are singular: two instances of the same /UNIT/
+instruction will be identical in terms of their binary.  On the other
+hand, two instances of the same /MULTI/ instruction may not be
+equivalent due to the operand they take.  Crucially, most if not all
+/MULTI/ instructions have different versions for each /data type/.