as: VAX-operands

 
 9.49.6 VAX Operands
 -------------------
 
 The immediate character is '$' for Unix compatibility, not '#' as DEC
 writes it.
 
    The indirect character is '*' for Unix compatibility, not '@' as DEC
 writes it.
 
    The displacement sizing character is '`' (an accent grave) for Unix
 compatibility, not '^' as DEC writes it.  The letter preceding '`' may
 have either case.  'G' is not understood, but all other letters ('b i l
 s w') are understood.
 
    Register names understood are 'r0 r1 r2 ... r15 ap fp sp pc'.  Upper
 and lower case letters are equivalent.
 
    For instance
      tstb *w`$4(r5)
 
    Any expression is permitted in an operand.  Operands are comma
 separated.