CALL began in the 1960s with mainframe-based drill and practice materials, especially those based on the University of Illinois' PLATO (Programmed Logic for Automated Teaching Operations) system.The Mac had built-in sound, making it easier to work with than PCs, which had incompatible proprietary boards competing with one another.Reasonably-priced authoring programs became available for PCs, and with the development of the Windows operating system for PCs and standardization of sound formats, the distinction between PC and Mac became less critical.Some teachers built assignments around student interactions in multi-user domains  (MUDs and MOOs), types of enriched chat environments.In the late 1980s and early 90s, the Apple Macintosh replaced the Apple II in many educational settings in the US and became an immediate favorite among teacher-developers because of the support of HyperCard, a powerful but easy-to-use authoring program.It was observed that building collaborative projects around the computer and using computer mediated communication (CMC) activities had a strong effect on some students' motivations and seemed to make it easier for shy students to become involved.Early programs were written by teacher-developers on Apple II, IBM PC, and BBC computers, and were often distributed for free.It remained an insignificant alternative for language learning outside of a few universities until the spread of the microcomputer into educational settings in the early 1980s.