| cshader | Visual Studio CShader Data |
| csharp | Visual C# Script |
| cshtml | Razor C# Web Page |
| csi | ContentServ CS EMMS Include |
| csi | CR10X EdLog Source Code |
| csig | SCons Content Signature |
| csl | Citation Style Language Document |
| cslog | CodeSite Log |
| csm | C++ Builder Precompiled Header |
| csn | Adobe Dreamweaver Code Snippet Data |
| csn | Dreamweaver Code Snippet File |
| cso | High Level Shader Language Compiled Bytecode |
| csp | InterSystems Cache Server Page |
| csp | RadGs Concept Server Page |
| cspkg | Microsoft Azure Service Package |
| csq | Microsoft Visual FoxPro Client-Server Query File |
| csx | Visual C# Script |
| ctc | Visual Studio Command Table Configuration |
| ctf | MATLAB Component Technology File |
| ctl | PDP-10 Batch File |
| ctl | Visual Basic User Control Text |
| cto | Visual Studio Binary Command Table Output |
| ctp | CakePHP Template |
| ctrace | Android System Trace Data |
| ctrl | Oracle WebLogic Workshop Controls |
| cts | ABC Permanent Locations Data |
| ctsym | Visual Studio Command Table Symbols File |
| ctx | Visual Basic User Control Binary File |
| ctxt | BlueJ Context File |
| cu | CUDA Source Code |
| cuf | Turbo C Utilities Form Definition |
| cuh | CUDA Header |
| cuo | CUDA Object |
| curl | Curl Applet |
| cv | Microsoft CodeView Data |
