.LIBRARY adds a name to the macro library list that is searched
    whenever a .MCALL or an undefined opcode is encountered. The
    libraries are searched in the reverse order in which they were
    specified to the assembler.

    If you omit any information from the macro-library-name file
    description, default values are assumed. The device defaults to
    your current default disk; the directory defaults to your current
    default directory; the file type defaults to MLB.