This is the Project Athena Zephyr notification system version 2.0. Zephyr allows users to send messages to other users or to groups of users. Users can view incoming Zephyr messages as windowgrams (transient X windows) or as text on a terminal. Zephyr can optionally make use of the Kerberos version 4 security library or the Hesiod service name resolution library. Please note that Zephyr version 2.0 is not compatible with previous versions of Zephyr, in two important ways. First, the inter-server brain dump protocol has changed, so a version 2.0 Zephyr server and an older Zephyr server will not be able to brain dump to each other. Second, Zephyr clients built from sources earlier than the January 3, 1995 snapshot will not be able to send authentic notices through version 2.0 Zephyr servers. Comments, suggestions, bug reports, or patches should go to bug-zephyr@mit.edu. To find out how to configure, build, and install Zephyr, read the file INSTALL. To find out how to operate a Zephyr service, read the file OPERATING. To find out how to use an existing Zephyr service, read the file USING. Please read the file NOTES before making any modifications to the source tree. LaTeX files for the Zephyr API are located on doc/progman. These documents may serve as a useful reference, but they have not been under recent maintenance, so they might have become somewhat out of date. --Greg Hudson ghudson@mit.edu