return_devnam

    OpenVMS usage:char_string
    type:         character-coded text string
    access:       write only
    mechanism:    by descriptor-fixed-length string descriptor
    Buffer to receive the device name. The return_devnam argument is
    the address of a character string descriptor pointing to a buffer
    into which $DEVICE_SCAN writes the name of the first or next
    device that matches the specified search criteria. The maximum
    size of any device name is 64 bytes.

 retlen

    OpenVMS usage:word_unsigned
    type:         word (unsigned)
    access:       write only
    mechanism:    by reference
    Length of the device name string returned by $DEVICE_SCAN. The
    retlen argument is the address of a word into which $DEVICE_SCAN
    writes the length of the device name string.

 search_devnam

    OpenVMS usage:device_name
    type:         character-coded text string
    access:       read only
    mechanism:    by descriptor-fixed-length string descriptor
    Name of the device for which $DEVICE_SCAN is to search. The
    search_devnam argument accepts the standard wildcard characters,
    the asterisk (*), which matches any sequence of characters, and
    the percent sign (%), which matches any one character. If the
    search_devnam argument does not include a wildcard character,
    an exact match is used for comparison. For example, to match all
    unit 0 DU devices on any controller, specify *DU%0. This string
    is compared to the most complete device name (DVI$_ALLDEVNAM).
    Only uppercase characters are accepted.

 itmlst

    OpenVMS usage:item_list_3
    type:         longword_unsigned
    access:       read only
    mechanism:    by reference
    Item list specifying search criteria used to identify the device
    names for return by $DEVICE_SCAN. The itmlst argument is the
    address of a list of item descriptors, each of which describes
    one search criterion. The list of item descriptors is terminated
    by a longword of 0.

    Refer to the VSI OpenVMS System Services Reference Manual to view
    the item code diagram and descriptor fields table.

 contxt

    OpenVMS usage:quadword_unsigned
    type:         quadword (unsigned)
    access:       modify
    mechanism:    by reference
    Value used to indicate the current position of a $DEVICE_SCAN
    search. The contxt argument is the address of the quadword that
    receives this information. On the initial call, the quadword
    should contain 0.