From the documentation:
WR-BBS is designed to operate on an IBM PC or compatible micro-
computer. It operates as a single-port system, but its database foundation
was designed to allow multi-port operation as a potential future
development. WR-BBS utilizes the fully-integrated W-TREE Database Manager
to rapidly locate and access database records, minimizing the "dead screen"
time that would otherwise occur when a database search occurs. The W-TREE
Database Manager is integrated at source code level for seamless operation
and maximum flexibility for third party developers.