| c3xml | Chem3D XML Format File |
| c4d | Maxon Cinema 4D Object |
| c4dlib | Maxon Cinema 4D Library |
| c4dupdate | Maxon Cinema 4D Update Data |
| c4p | CrossOver v9 C4P Installer |
| c64 | PC64 Saved Session |
| ca | OpenSSL Certificate Authority Data |
| ca | Initial Telnet Cache |
| ca1 | STABCAL Calculation Data |
| ca2 | STABCAL Calculation Data |
| ca3 | STABCAL Calculation Data |
| ca3 | Casio WK-1800 Save All Data |
| ca4 | STABCAL Calculation Data |
| cabal | Haskell Cabal Data |
| cache-2 | VLC Media Player Font Cache |
| cache-3 | VLC Media Player Font Cache |
| cae | Abaqus/CAE Model Database |
| cag | Microsoft ClipArt Gallery Database |
| cah | Ulead Photo Explorer Thumbnail Cache |
| cal | Radiance Function File |
| cal | Keysight PLTS Calibration Data |
| cal | Lego Mindstorms NXT Sensor Calibration Data |
| cal3d | Cal3D Data |
| caldb | HEASARC Calibration Database |
| calibre | Calibre Device Information Data |
| cam | Minolta Vivid 3D Scanner Camera Data |
| cam | PC 1000 Calculation Method Data |
| cam-ft | CircuitCAM Footpring Library |
| cam-gmc | CircuitCAM GMC Library |
| camp | WCS Color Appearance Model Profile |
| camt | SEPA CAMT Data |
| cap | Libpcap Captured Packets |
| caps | CaptureSaver Knowledge Base |
| capt | Linrock Capito Data |
| car | PC 1000 Calculation Result Data |