anchor.diff:  
   ;;; Test instructions
   
  -(defparameter *test-instructions* #(#x40 #x40 #x05 #x03 #x00 #x91 #xb0 #xff #x04 #x01 #x72 #x04 #x50 #x5a #x51 #x52 #x48 #xff #b11001011 #x43 #x74 #x03 #xbe #x02 #x03 #x01 #b11001111 #x47 #x83 #b11000111 #xfe #xf4) "Test instructions")
  +(defparameter *test-instructions* #(#x40 #x40 #x05 #x03 #x00 #x91 #xb0 #xff #x04 #x01 #x72 #x04 #x50 #x5a #x51 #x52 #x48 #xff #b11001011 #x43 #x74 #xfd #xbe #x02 #x03 #x01 #b11001111 #x47 #x83 #b11000111 #xfe #xf4) "Test instructions")
  
positive.code:   `(case (mod ,opcode 4)
      (0 (,operation (next-instruction-ahead-of-indirect-address ,mod-bits ,r/m-bits) (indirect-address ,mod-bits ,r/m-bits nil) nil))
      (1 (,operation (next-word-ahead-of-indirect-address ,mod-bits ,r/m-bits) (indirect-address ,mod-bits ,r/m-bits t) t))
      (3 (,operation (sign-extend (next-instruction-ahead-of-indirect-address ,mod-bits ,r/m-bits)) (indirect-address ,mod-bits ,r/m-bits t) t))))
  
  (defmacro parse-group1-opcode (opcode)
    `(parse-group-opcode
  
negative.code:   "Loop through loaded instructions."
    (loop
       for ret = (parse-opcode (next-instruction))
       collecting *ip* into ips
       until (equal ret '("hlt"))
       do (advance-ip)
       finally (return ips)))
  
  (defun disasm-instructions (instr-length)
    "Disassemble code."
  