High Quality Content by WIKIPEDIA articles! TOPS (Transcendental OPerating System) is a peer-to-peer LAN-based file sharing system best known in its Macintosh implementation, but also available for Windows and able to interoperate with Unix`s NFS. Originally written by Centram Systems West, the company was purchased by Sun Microsystems as part of Sun`s development of the NFS ecosystem. Sales of TOPS dried up after the introduction of System 7, which featured a similar file sharing system built-in, and Sun spun off their NFS developments to Sitka.