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The bit-vector instruction set. More CISCy than CISC.
Haskell Assembly
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The bit-vector instruction set. More CISCy than CISC.

BISC is an experimental hypothetical CISC instruction set that operates on bits as its atomic storage unit instead of bytes. I wrote this for a CS441 Computer Architecture class in Fall 2009.


See the included 1337.asm and loopio.asm for examples. The code is assembled from plaintext with lots of comments so it should be easy to figure out.


Instructions start with ..

  • For a list, see the instDefs part of BISC.hs

Registers start with $.

The special registers are:

  • $ip for the instruction pointer
  • $out for the output buffer
  • $in for the input buffer

The other registers are:

  • $a through $z,
  • $α through $ω (alpha through omega)

Labels start with * to denote a label, and & to use a previously-defined label as a location to jump to.

Constants start with

  • b for binary strings of any length
  • B for 8 bit bytes in integer order
  • c for 8 bit bytes in character order
  • i for 32-bit integers
  • " for an ascii string (terminated on whitespace)


  • Instructions are any size for better potential huffman coding! Save every bit! Unless it's too hard, then forget it.
  • Registers are infinite bit vectors! This would make this instruction set hard/impossible to implement in hardware probably, but that is somebody else's problem. Also, unicode registers!
  • Labels can be set and jumped to! Structured programming!
  • Instructions can have dynamic arity! With precision to the bit! They can specify how many bits they need for arguments at runtime!
  • There is a stack of registers to create lexical closures! These are not implemented fully yet but could be made to work easily. The programmer need not worry about a function call's side effects on the registers. Proper isolation!


  • It's really complex. It'd be much worse in C. Blame the deadline for some of the ugliness. As an aside, Hindley-Milner type inference is really tremendously useful when putting together big projects in a short amount of time.

  • The implementation is very fargone and abstracted away from any actual raw bit twiddling. This is arguably a good thing!

  • Modern optimizations would be really hard to implement. Some ancient optimizations for non-Von Neumann architectures will probably work well enough however.

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