laser printers, 8 bit output and fflow control

[Robert Morris]

Yes, the Apple implentation of PostScript, and perhaps other
implementations, pass back error messages from the
host at least on the serial line. They are only slightly more
informative than those from most C compilers (ratifying Reid's
recent linguistic analogies) but certainly are helpful if
you know what you are trying to accomplish but don't know
why it isn't working.