anchor.diff:  
   (defun bits->byte-reg (bits)
     (elt +bits-to-byte-register+ bits))
  +
  +(defun bits->segment (bits)
  +  (elt +bits-to-segment+ bits))
   
   (defmacro default-seg-to (default &optional (current *current-segment*))
     `(if (null ,current) ,default ,current))
  
positive.code: (defconstant +byte-register-to-word+ '(:al (:ax nil) :ah (:ax t) :bl (:bx nil) :bh (:bx t) :cl (:cx nil) :ch (:cx t) :dl (:dx nil) :dh (:dx t)) "Mapping from byte registers to word registers")
  (defconstant +bits-to-register+ '(:ax :cx :dx :bx :sp :bp :si :di) "Mapping from index to word register")
  (defconstant +bits-to-byte-register+ '(:al :cl :dl :bl :ah :ch :dh :bh) "Mapping from index to byte register")
  
  ;;; Constant mappings
  
  
negative.code:     ((= opcode #x2e) (segment-prefix :cs))
      ((= opcode #x36) (segment-prefix :ss))
      ((= opcode #x3e) (segment-prefix :ds))
      ((= opcode #x8c) (mov-segment-to-indirect))
      ((= opcode #x8e) (mov-indirect-to-segment))
      ((= opcode #xe9) (jmp-near))
      ((= opcode #xeb) (jmp-short))
      ((in-paired-byte-block-p opcode #x70) (jmp-short-conditionally opcode (flag-p :of) "o"))
  