| 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 | MPLAB IDE COF File |
| cof | Common Object File |
| coffee | CoffeeScript JavaScript File |
| cola | Cola Language Source Code |
| comb | Amazon Lumberyard Blend Space Combination Data |
| com_ | Emu8086 Assembly Source Code |
| conc | Concurnas Source Code |
| container | Eclipse IDE Project Settings Data |
| cord | Visual Studio Cord Data |
| core | Linux Core Dump Data |
| cos | Scilab Binary Diagram |
| cosf | Scilab ASCII Diagram |
| counter | NetObjects Fusion Components Bbscomp Message |
| coverage | Visual Studio Code Coverage Data |
| cox | Click and Create Extension Object |
| cpb | CPB Data |
| cpdsc | CMSIS Pack Project Description |
| cpf | Cab Provisioning Format |
| cphd | CloudChan Pre-processed Hypertext Document |
| cpk | Novell Netware Compiled Server Software Package |
| cpl | Concordance Desktop Programming Language Script |
| cplist | GNU Make C Property-list Data |
| cplusplus | C++ Source Code |