The VR Juggler Portable Runtime (VPR) provides the Juggler Project with an operating system abstraction layer. By using this abstraction, the process of creating cross-platform software is simplified. Programmers use an object-oriented API that is consistent across all platforms. Included in the API is support for threads, synchronization primitives, sockets, and serial I/O. Supported platforms include IRIX, Linux, FreeBSD, Win32, Mac OS X, HP-UX, and Solaris.