This is a shared library that goes in your System Folder/Extensions folder along with DigiSystem(tm) INIT 5.0.1. It is needed for third-party Mac OS applications that use Direct I/O to access Digidesign hardware.Before the release of 5.0.1, the Direct I/O library was part of DSI. With 5.0.1 we have separated out the Direct I/O library from DSI, so you now need them both in your Extensions Folder. This version of the Direct I/O library also has a fix in it for 882|20 users who were seeing double occurrences in the peripheral list.Download Software and Read Me at www.digidesign.com