| cmp | Heliosoft Seismaster Colormap File |
| cmp | KiCad Parts-to-module Assignments Data |
| cmp7 | Araxis Merge Comparison Data |
| cmpd | Chemnum Compounds Data |
| cmplib | Altium Designer Component Library |
| cmpt | Cesium Composite Tile Data |
| cmr | Coach Results File |
| cmrbk | CaseMap ReportBook Definition Data |
| cmt | E-Sword v8 Commentary Data |
| cmtx | E-Sword v9 Commentary Data |
| cmw | Custom Maintenance Wizard Data |
| cmxl | Microsoft Pivot Collection Data |
| cmz | Poser Compressed Camera Data |
| cn | GenePattern Copy Number Data |
| cnb | Pegasus Mail Noticeboard Message |
| cnc | QuickCAM Pro CNC Machine Tool Path |
| cndf | Compressed NDF File |
| cne | Ancora Conserved Noncoding Elements Data |
| cng | CryptoNG Encrypted File |
| cni | CWBench Data |
| cnj | Acharya Conjunct Data |
| cnm | Pegasus Mail New Message |
| cnn | CNVkit Data |
| cnu | iiV Lookup Script |
| cnv | Tekla Structures Conversion File |
| cnv | PLINK Segmental Copy Number Variant Data |
| cnw | DSC Crossover Network Tuning Data |
| cnx | Trimble LM80 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 |