| cphd | CloudChan Pre-processed Hypertext Document |
| cpk | Novell Netware Compiled Server Software Package |
| cplusplus | C++ Source Code |
| cpp | C++ Source Code |
| cpz | LoseThos C+ Source Code |
| cr | CRiSP Macro File |
| cr1 | CRBasic Source |
| cr2 | CRBasic Source |
| cr3 | CRBasic Source |
| cr4 | CRBasic Source |
| cr5 | CRBasic Source |
| cr6 | CRBasic Source |
| cr7 | CRBasic Source |
| cr8 | CRBasic Source |
| cr9 | CRBasic Source |
| crash | Mac OS X Crash Log |
| crf | MASM Cross-Reference Data |
| crn | Crunch Compressed Texture |
| cs | Visual C# .NET Class |
| csc | Ovation Pro C Script |
| csdef | Microsoft Azure Service Definition Schema |
| cshtml | Razor C# Web Page |
| csi | CR10X EdLog Source Code |
| csig | SCons Content Signature |
| csl | Citation Style Language Document |
| cslog | CodeSite Log |
| csm | C++ Builder Precompiled Header |
| csn | Dreamweaver Code Snippet File |
| csp | RadGs Concept Server Page |
| csp | InterSystems Cache Server Page |
| csq | Microsoft Visual FoxPro Client-Server Query File |
| csx | Visual C# Script |
| ctc | Visual Studio Command Table Configuration |
| ctf | MATLAB Component Technology File |
| ctl | Visual Basic User Control Text |
