fab
    OpenVMS usage:fab
    type:         unspecified
    access:       modify
    mechanism:    by reference
    File access block (FAB) used with LIB$FILE_SCAN. The optional fab
    argument is the address of the FAB that contains the address and
    length of the file specification.
 context
    OpenVMS usage:context
    type:         longword (unsigned)
    access:       modify
    mechanism:    by reference
    Temporary default context used in LIB$FILE_SCAN. The optional
    context argument is the address of a longword containing this
    temporary default context.