| con | Acharya Consonant Data |
| con | ALEID2000 Contour Data |
| con | BI/Query Connection File |
| con | KJT-200 Constituent Data |
| con | SQL Script Constraints |
| con | USoft Conceptual Schema Data |
| conf-auto | WOW! Diagnostic Configuration Data |
| conform | Conformalizer Change List |
| conl | PJM CONL Data |
| conp | SynTest Design Connectivity Information |
| consis | Sciral Consistency Document |
| cont | Panasonic Camcorder Metadata |
| contact | Windows Vista Contacts Data |
| contacts | Windows Vista Contacts Data |
| control | HEC-HMS Control Specifications Data |
| coo | Tajima Embroidery Data File |
| cook | Netscape for Mac Cookie Data |
| cookie | HTTP Cookie Data |
| cool | QB - Text Analyzer Vocabulary Data |
| coords | Ribbons Coords Data |
| cor | CYANA DG Cartesian Coordinate File |
| cor1 | Corel Multimedia Manager Data |
| cos | Scilab Xcos Diagram Data |
| cosf | Scilab Xcos Diagram Data |
| costyle | Capture One Style Data |
| cov | RFM Covariate Table |
| covsym | Gumshoe Coverage Symbols Data |
| cow | Cowsay Data |
| coz | EFILive Calibration Data |
| co_ | Compressed COM File |
| cp1 | CARE-S InfoWorks Phosphorus Detail Data |
| cp4 | Adobe Captivate 4.0 Simulation Data |
| cpa | Cadstar PCB Design |
| cpaa | Adobe Captivate Shared Action Data |
| cpao | 3Dize Cool Page Objects Counter Data |