| c3d2 | Chem3D Cartesian 2 Data |
| c3e | Cype Data |
| c3l | CommView License Data |
| c3t | Chem3D Template File |
| c3xml | Chem3D XML Format File |
| c3z | OpenQwaq 3D Model |
| c4d | Maxon Cinema 4D Object |
| c4dlib | Maxon Cinema 4D Library |
| c4dupdate | Maxon Cinema 4D Update Data |
| c4p | CrossOver v9 C4P Installer |
| c64 | Commodore 64 ROM Image |
| c64 | PC64 Saved Session |
| c8k | CHIP-8 Keyboard Data |
| ca | DATAIR FlexPlus Data |
| ca | Initial Telnet Cache |
| ca | OpenSSL Certificate Authority Data |
| ca1 | STABCAL Calculation Data |
| ca2 | STABCAL Calculation Data |
| ca3 | Casio WK-1800 Save All Data |
| ca3 | STABCAL Calculation Data |
| ca4 | STABCAL Calculation Data |
| ca5 | STABCAL Calculation Data |
| ca6 | STABCAL Calculation Data |
| ca7 | STABCAL Calculation Data |
| cabal | Haskell Cabal Data |
| caccrt | CACAO Cartesian Chemical Modeller Data |
| cache-2 | VLC Media Player Font Cache |
| cache-3 | VLC Media Player Font Cache |
| cache2 | Pro/ENGINEER Cached Data |
| cachedmsg | Valve Steam Cache Data |
| cachedump | Cachedump Data |
| cadpac | CADPAC Chemical Modeller Input Data |
| cae | Abaqus/CAE Model Database |
| cag | Microsoft ClipArt Gallery Database |
| cah | Ulead Photo Explorer Thumbnail Cache |
