| bwu | BlindWrite CD Copier Data |
| bxa | LogiBlox Signal Aliasing Information Data |
| bxd | Broken X Disk Manager Database |
| bxf | iPed Breeder eXchange Format Data |
| bxi | Blaise Datamodel Properties |
| bxml | Bean XML Data |
| bxs | BioExplorer Session Data |
| bxw | Pedigree Central Database Index |
| by | PSpice Data |
| bz1 | WinTOTAL Automatic Backup Data |
| bzf | Tobii Dynavox Compass User Data |
| bzx | SIR 4000 Quick3D Grid Assembly Data |
| c1 | POV-Ray Include File |
| c10 | IRIG 106 Original Recording Data |
| c1b | Digital Tachograph Data |
| c1w | Capture One Work Data |
| c2 | POV-Ray Include File |
| c21 | CARE-S InfoWorks Defined Pollutant Detail Data |
| c2e | NJStar Chinese WP Dictionary Index |
| c2o | Titan Capture Visualiser Data |
| c2r | Windows Media Center Click-to-record File |
| c2s | G7 Click2Stitch Embroidery Design |
| c2v | WellSight Systems HASP SRM License Information Data |
| c3d | Coordinate 3D Data |
| c3d | Chem3D Template File |
| c3e | Cype Data |
| c3t | Chem3D Template File |
| 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 |