The Assign Channel with Mailbox routine assigns a channel to a
    specified device and associates a mailbox with the device. It
    returns both the device channel and the mailbox channel.

    Format

      LIB$ASN_WTH_MBX  device-name [,maximum-message-size]

                       [,buffer-quota] ,device-channel

                       ,mailbox-channel

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2  –  Arguments

 device-name

    OpenVMS usage:device_name
    type:         character string
    access:       read only
    mechanism:    by descriptor

    Device name that LIB$ASN_WTH_MBX passes to the $ASSIGN service.
    The device-name argument is the address of a descriptor pointing
    to the device name.

 maximum-message-size

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       read only
    mechanism:    by reference

    Maximum message size that can be sent to the mailbox; LIB$ASN_
    WTH_MBX passes this argument to the $CREMBX service. The maximum-
    message-size argument is the address of a signed longword integer
    containing this maximum message size.

 buffer-quota

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       read only
    mechanism:    by reference

    Number of system dynamic memory bytes that can be used to buffer
    messages sent to the mailbox; LIB$ASN_WTH_MBX passes this
    argument to the $CREMBX service. The buffer-quota argument is
    the address of a signed longword integer containing this buffer
    quota.

 device-channel

    OpenVMS usage:word_unsigned
    type:         word integer (unsigned)
    access:       write only
    mechanism:    by reference

    Device channel that LIB$ASN_WTH_MBX receives from the $ASSIGN
    service. The device-channel argument is the address of an
    unsigned word integer into which $ASSIGN writes the device
    channel.

 mailbox-channel

    OpenVMS usage:channel
    type:         word integer (unsigned)
    access:       write only
    mechanism:    by reference

    Mailbox channel that LIB$ASN_WTH_MBX receives from the $CREMBX
    service. The mailbox-channel argument is the address of an
    unsigned word integer into which $CREMBX writes the mailbox
    channel.