These are examples of algorithms written in PlusCal, the algorithm language for Leslie Lamport's TLA+ algorithm specification system.
These have been created in the TLA+ Toolbox, so most of the files are supporting files for running in the Toolbox and using the TLC algorithm verification checker.
The important (non-auto-generated) files for review are those that end in .tla, such
as Euclid/Euclid.tla and HourClock/HourClock.tla.
I've written the part above the line \* BEGIN TRANSLATION and the PlusCal code falls
between the (* and *) comment markers, starting with the --algorithm XXX indicator.