| cls | Visual Basic Class Module |
| clw | Clarion Source Code |
| clw | Visual Studio ClassWizard Data |
| clz | Crestron SIMPL Library Data |
| cma | OCaml Library |
| cmake | CMake Script |
| cmbx | SharpDevelop Combine File |
| cmc | Crestron SIMPL Module |
| cmd | PTC Creo CL Commands Data |
| cmi | OCaml Compiled Interface |
| cml | ProWorx NXT Comment Data |
| cmn | Visual Studio Windows CE Build Settings |
| cmo | OCaml Compiled Bytecode |
| cmt | OCaml CMT Data |
| cmti | OCaml CMT Data |
| cmxa | OCaml Library |
| cntk | Microsoft CNTK Data |
| cnut | Squirrel Compiled Bytecode |
| cobol | Micro Focus COBOL Source Code |
| cod | µVision Complete Program Listing Data |
| codaplugin | Coda Plug-in |
| codasite | Coda Site Data |
| cof | Common Object File |
| cof | MPLAB IDE COF File |
| coffee | CoffeeScript JavaScript File |
| cola | Cola Language Source Code |
| comb | Amazon Lumberyard Blend Space Combination Data |
| comp | CodeWarrior Compiler Data |
| com_ | Emu8086 Assembly Source Code |
| conc | Concurnas Source Code |
