The Santa Cruz Operation Inc has gone to Santa Monica-based Retix Inc for local and wide-area Open Systems Interconnection software for use with its SCO Unix System V/386 and SCO Xenix operating systems for personal computers, and as an add-on product for the Santa Cruz Open Desktop, integrated graphical Unix front end. Santa Cruz will offer full seven-layer Open Systems applications, including file transfer access and management and X400 message handling and Retix looks for over $10m between now and 1994 from the agreement. The software will enable customers for the operating systems to conform to GOSIP requirements on government contracts as well as meeting increasing end-user commercial demand for Open Systems Interconnection compliance. The open systems communications software will run concurrently with existing Santa Cruz networking packages, including TCP/IP and Xenix-Net on the same processor.