The ".c 2" file is an archive that contains all of the individual job files. When these individual job files are extracted, the ".c 2" file is deleted.

The ".c 2" archive is generated from the individual files when:
a) you change jobs
b) you completely shut down CAESAR II

Once the ".c 2" archive is created, then the individual job files are deleted.

IMPORTANT:
When working in a shared folder, make sure everyone sets their "User ID" in the configuration of their workstation. This will keep people from stepping on each other's communication files in the working directory.