Afaik there exists no BIOS call that makes use of the bidirectional parallel port and my books which are also old show no such thing. I think that the Windows API has a set of calls that deal with this, in conjunction with some driver DLL or other, which is used for parallel port connected external devices. Peter -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu