/sys$common/syshlp/helplib.hlb RTL Routines, LIB$, LIB$ICHAR, Argument  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 source-string

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

    Source string whose first character is converted to an integer
    by LIB$ICHAR. The source-string argument is the address of a
    descriptor pointing to this source string.