lp(HW)                          19 June 1992                          lp(HW)


 Name

    lp, lp0, lp1, lp2 - line printer device interfaces

 Description

    The lp0, lp1, and lp2 files provide access to the optional parallel ports
    of the computer.  The lp0 and lp2 files provide access to parallel ports
    1 and 2, respectively.  The lp1 file provides access to the parallel port
    on the monochrome adaptor.

    Only one of lp0 and lp1 may be used on a given system. To access two
    parallel printers on a system, use either lp0 or lp1, and lp2.

    The minor device numbers of the lp special files are used to control the
    behavior of the parallel port driver. Three bits may be set in the minor
    device number, with the following effects:

    Bit 7   Reset printer on each open.

    Bit 6   Force polling, rather than interrupts and polling (as normal).
            This setting is provided for situations when the printer appears
            to be running slowly as a result of lost interrupts.

    Bit 5   Tandy printer translation.  This setting is provided to perform
            translation for driving Tandy printers. Firstly, all standard
            output post-processing is turned off. (This is equivalent to stty
            -opost.) Secondly, tabs and formfeeds are expanded at the driver
            level. (Tabs are expanded to 8-column tabstops; formfeeds are
            expanded to 66 lines per page, using carriage returns: the page
            length may be changed using an ioctl(S) call. Line count and
            printhead position are tracked to enable the driver to expand
            tabs and formfeeds correctly.)  Thirdly, the character following
            a backspace is never translated or acted on in any way except to
            output it. (Tabs and formfeeds are not expanded; returns and new-
            lines do not increment the line count and other characters do not
            increment the printhead position.)

            This type of behavior is required to support certain Tandy print-
            ers. It is not required in any other circumstances, and should
            not normally be used.

 Files

    /dev/lp0?
    /dev/lp1?
    /dev/lp2?

    where the ? is optional and may be any one of the following:

    i  Reset on open

    p  Force polling

    f  Tandy printer translation

 See also

    lp(C), lpadmin(ADM), lpsched(ADM), parallel(HW)

 Notes

    The standard lp ports, lp0, lp1, and lp2 send a printer initialization
    string the first time the file is opened after the system is booted.

    Not all computers have an alternate parallel port slot.