Files with the .cos (Creatures Object Source code) extension are CAOS source code files, which contain CAOS scripts/code in plain text. The scripts which compose a large portion of Creatures 3 and Docking Station are stored in .cos files. These files are normally found in the Bootstrap/ directory in the game folder. They can be injected using the JECT CAOS command.
Did you know? Alexander Laemmle invented the cos file.