| cmdb | CFX Mesh Database |
| cmdf | CrystalMaker V2 Data File |
| cmdl | Cafu Engine Model Data |
| cmf | CIFMIF File |
| cmh | PLINK Cochran Mantel Haenszel 2x2xK Test Report |
| cmh2 | PLINK Cochran Mantel Haenszel IxJxK Test Report |
| cmj | ControlMyJoystick Profile |
| cml | Chemical Markup Language File |
| cml | CryptoMailer Encrypted File |
| cmm | Corel Multimedia Manager v7 Album |
| cmn | Microsoft SMS Collection Membership Update |
| cmod | Celestia Model |
| cmp | Heliosoft Seismaster Colormap File |
| cmp | General CADD Component Data |
| cmp | KiCad Parts-to-module Assignments Data |
| cmpd | Chemnum Compounds Data |
| cmplib | Altium Designer Component Library |
| cmr | Coach Results File |
| cmt | E-Sword v8 Commentary Data |
| cmtx | E-Sword v9 Commentary Data |
| cmw | Custom Maintenance Wizard Data |
| cmz | Poser Compressed Camera Data |
| cn | GenePattern Copy Number Data |
| cn1 | CNR Modem Initialization 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 |
