| cis | CheckInbox Settings |
| cli | QIP Contact List Invisible Data |
| clr | Autodesk 3D Studio MAX Color Definitions |
| clr | WinBatch Studio Syntax Color Customization |
| clv | QIP Contact List Visible Data |
| cm | Cable Modem Configuration |
| cmate | ControllerMate Data |
| cmclc | CET Designer Calculation View Settings Data |
| cmlight | CET Designer Light Settings Data |
| cmp | WinBatch Studio Compilation Settings |
| cmpvs | CET Designer Visibility Settings Data |
| cms | Connection Manager Service Provider Data |
| cms | Casio WK-3000 Song Sequencer |
| cmtbx | CET Designer Component Tab Settings Data |
| cn3 | Cn3D Data |
| cn3d | Cn3D Data |
| cnf | Configuration File |
| cnf | Origin Configuration File |
| cns | Client Connection Manager Config |
| cntl | GoCart Control Data |
| con | Configuration File |
| conf | Configuration File |
| config | Configuration File |
| controls | OpenBVE Keyboard Shortcuts |
| copreset | Capture One Preset Data |
| cos | Capture One Settings |
| cpf | Curtis Programmer Settings |
| cpff | Cam2Com Capture Properties |
| cpm | Cisco Secure Policy Manager Settings |
| cq | CQUAL Configuration |
