[2] DUCS differed from competing products such as Westi and IBM's own CICS in that it was subordinate to the application's mainline program.
Westi, for example, was the mainline program and users wrote subroutines to read and write data to and from terminals and discs.
DUCS reversed that model in that it was, in fact, a subroutine package that read from and wrote to monitors, both local and remote.
Its popularity made him realize it had potential as a commercial product, and he left IBM about 1970, and incorporated in Brookline, Massachusetts as CFS, Inc.
Lundin wrote games in Fortran and Assembler and Goran in COBOL to demonstrate the API for programmers.