The Convert Numeric Text to Binary routines return a binary
    representation of the ASCII text string representation of a
    decimal, hexadecimal, or octal number.

    Format

      LIB$CVT_DTB  byte-count ,numeric-string ,result

      LIB$CVT_HTB  byte-count ,numeric-string ,result

      LIB$CVT_OTB  byte-count ,numeric-string ,result