The Length of String Returned as Longword Value routine returns
    the length of a string.

    Format

      LIB$LEN  source-string

1 - Returns

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

    Length of the source string, extracted and zero-extended to 32
    bits.

2 - Argument

 source-string

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

    Source string whose length is returned by LIB$LEN. The source-
    string argument contains the address of a descriptor pointing to
    this source string.