| cnv | PLINK Segmental Copy Number Variant Data |
| cnv | Tekla Structures Conversion File |
| cnw | DSC Crossover Network Tuning Data |
| cnx | IBM Rational XDE Component Instance File |
| cod | WindLDR Binary PLC Data |
| codec | Rockbox Codec |
| coe | Xilinx CORE Generator Coefficients |
| cof | LightCycler v4 Coefficient Data |
| cog | SolidWorks Enterprise PDM Copied Log |
| collection | Adobe Bridge Collection Data |
| color | Ribbons Color Mapping |
| colors | SAM Makelogo Colors Data |
| comicstl | Comic Life 2 StyleSheet Data |
| comment | Geomview Comment Object Data |
| compo | DAZ 3D Carrara Pro Temporary Data |
| con | BI/Query Connection File |
| con | USoft Conceptual Schema Data |
| con | SQL Script Constraints |
| con | KJT-200 Constituent Data |
| con | Acharya Consonant Data |
| conl | PJM CONL Data |
| conp | SynTest Design Connectivity Information |
| 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 |
| cookie | HTTP Cookie Data |
| cool | QB - Text Analyzer Vocabulary Data |
| coords | Ribbons Coords Data |
