| cpt | Casio WK-1800 Pattern Sequerncer Pattern |
| cpt | Mail.dat Component File |
| cpt2 | M-Tron Pro Library |
| cptl | Adobe Captivate 5 Template |
| cptm | Adobe Captivate Theme Data |
| cpu | SiSoftware Sandra File |
| cpv | Serena PVCS Logfile |
| cpw | GP-Pro EX Library |
| cpx | Character Set Translation Table |
| cpxml | IBM ABLE Conversation Policies XML |
| cp_ | Compressed CPL File |
| cqcn | Chimera Tool Data |
| cqe | Cumulus 6 Query Export Data |
| cqf | PCAnywhere Command Queue Data |
| cql | XDCC Catcher Queue List |
| cqs | ConQuest Saved Search File |
| cqt | Mail.dat Container Quantity Data |
| cr0 | Autodesk Moldflow Cool Analysis Restart File |
| cr2 | Poser Character |
| cr3 | Casio WK-1800 Registration Data |
| cr4 | STABCAL Calculation Data |
| cram | CRAM Data |
| crashed | AbiWord Crash-Saved Document |
| crate | Serato DJ Crate Data |
| crc32 | CRC32 Checksum |
| crd | Carlson 2016 Coordinate Data |
| crd | CHARTrunner Dashboard |
| crd | CARE-S InfoWorks Catchment Runoff Data |
| crdb | Carlson 2016 Coordinate Database |
| crds | Windows CardSpace Backup |