| cl5 | Roxio Easy CD Creator 5 Project |
| clg | Collage Maker Project |
| clk | Corel R.A.V.E Project |
| cmmcd | Camtasia Studio MenuMaker Project |
| cmmp | Camtasia MenuMaker Project |
| cmmtpl | Camtasia MenuMaker Template |
| cmproj | Camtasia for Mac Project |
| cna | Catena Project |
| cnp | Bentley CONNECT Project |
| cp | Adobe Captivate Project |
| cpf | Cognos Framework Manager Project |
| cpj | WinOnCD Project |
| cpmz | Miradi ConPro Exported Project |
| cproj | Atmel Studio AVR GCC Project |
| cproject | Eclipse CDT Project |
| cptx | Adobe Captivate 5 Project |
| cpvc | Adobe Captivate Video Composition |
| csdproj | Visual Studio .NET Visual C# Smart Device Project |
| csproj | Visual Studio .NET Visual C# Project |
| ctd | Sony ClickToDvd Project |
| ctk | TeKton3D Project |
| ctproject | CrazyTalk Animator Project |
| ctv | Citavi Project |
| ctv3 | Citavi 3 Project |
| cwp | Cakewalk Sonar Project |
| cwprj | CanvasWorkspace Project |
| cxp | CX-Programmer Project |
| cyc | CYCAS CAD Project |
| cyg | Ashampoo Home Designer Project |
| cyp | Home Designer Pro Project |
