context

    OpenVMS usage:context
    type:         quadword (unsigned)
    access:       modify
    mechanism:    by reference

    Context specifier. The context argument is the address of an
    unsigned quadword used to keep the scan context for finding the
    next valid zone. The context argument must be 0 to initialize the
    scan and to start with the first returnable zone identifier.

 zone-id

    OpenVMS usage:identifier
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by reference

    Zone identifier. The zone-id argument is the address of an
    unsigned quadword that receives the zone identifier for the next
    zone.