source-string

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

    Source string (ASCII) to be translated by LIB$TRA_ASC_EBC. The
    source-string argument contains the address of a descriptor
    pointing to this source string.

 byte-integer-dest-string

    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor

    Destination string (EBCDIC). The byte-integer-dest-string
    argument contains the address of a descriptor pointing to this
    destination string.