Stream files follow the same rules as any other charmm input. One of those rules is the ability to embed data structures, using the file structure required, to read coordinates, residue sequences, or in this case, an RTF with residue topology descriptions. The distributed toppar_*.str files that extend the CHARMM force field with additional molecules use this feature. See the 'rtop' info file for a complete description of the RTF format.

Rick Venable
computational chemist