| .CPN | Microsoft Corporation | Arquivos de dados | Age Of Mythology Campaign File | Microsoft Age of Empires | Ensemble Studios |
| .CPO | Corel Corporation | Arquivos de dados | Corel Print House Data | Corel Print House | Corel |
| .CPQ | Compaq | Arquivos de dados | Compaq OEM Disc Configuration File | Microsoft Notepad | Microsoft Corporation |
| .CPW | Alexander V. Ilyin | Arquivos de dados | Online Cost Planning Service Cost Planning Work Data | Online Cost Planning Service | Alexander V. Ilyin |
| .CQP | IntelliQuilter | Arquivos de dados | CompuQuilter Pattern | CompuQuilter | IntelliQuilter |
| .CQQ | Kjartan Osmundsen | Arquivos de dados | Cool Quiz | Cool Quiz | Kjartan Osmundsen |
| .CQZ | CornEmpire Software | Arquivos de dados | Cool Quiz Quiz File | Cool Quiz for Windows | CornEmpire Software |
| .CR4 | Dr. Hsin H. Huang | Arquivos de dados | STABCAL Data File | STABCAL | Dr. Hsin H. Huang |
| .CR7 | Campbell Scientific | Arquivos de dados | CRBasic Source Code File | CR300-Series Dataloggers | Campbell Scientific |
| .CRACK | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .CRASH | Apple | Arquivos de dados | Mac OS X Crash Log File | Apple TextEdit | Apple |
| .CRD | Open Source | Arquivos de dados | Guitar Tabs | Notepad++ | Don Ho |
| .CRF | Open Source | Arquivos de dados | Cal3D Binary Materials File | Cal3DViewer | Open Source |
| .CRN | Unknown Developer | Arquivos de dados | Tree Ring Data File | Unknown Software | Unknown Developer |
| .CRO | FAO | Arquivos de dados | CropWat Data | CropWat | FAO |
| .CRS | Open Source | Arquivos de dados | StepMania Course File | StepMania | Open Source |
| .CRTX | Microsoft Corporation | Arquivos de dados | Office 2007 Chart Template File | Microsoft Excel | Microsoft Corporation |
| .CRUNCH | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .CRW | Canon Inc. | Arquivos de dados | Canon Raw CIFF Image File | MacPhun ColorStrokes | Macphun |
| .CS | Microsoft Corporation | Arquivos de dados | C# Source Code File | Notepad++ | Don Ho |
| .CSA | Agilent Technologies | Arquivos de dados | PNA Code Calset File | PNA Code | Agilent Technologies |
| .CSC | Corel | Arquivos de dados | Corel Script File | Corel Photo-Paint | Corel |
| .CSD | Valve | Arquivos de dados | Steam Game Data Backup File | Steam | Valve |
| .CSE | Macropool | Arquivos de dados | Web Research Document Package | Web Research Professional | Macropool |
| .CSHADER | Microsoft Corporation | Arquivos de dados | Microsoft Visual Studio Text Data | Microsoft Visual Studio | Microsoft Corporation |
| .CSK | Apple | Arquivos de dados | ClarisWorks Data | Apple AppleWorks | Apple |
| .CSL | Interscape | Arquivos de dados | CineStyle Color Lookup File | CineStyle Color Assist | Interscape |
| .CST | Smith Micro Software | Arquivos de dados | Manga Studio Story File | Manga Studio | Smith Micro Software |
| .CSV | Unknown Developer | Arquivos de dados | Comma Separated Values File | Microsoft Excel | Microsoft Corporation |
| .CS_ | Unknown Developer | Arquivos de dados | Creativ Compressed Sb16 Sbide File | Unknown Software | Unknown Developer |
| .CT0 | Tajima Group | Arquivos de dados | Tajima TBF Condition Data | DG/ML | Tajima Group |
| .CT1 | Microsoft Corporation | Arquivos de dados | Microsoft Systems Management Server Proposed Site Control Data | Microsoft Systems Management Server | Microsoft Corporation |
| .CT3 | Microsoft Corporation | Arquivos de dados | Microsoft Systems Management Server (SMS) Control File | Microsoft Systems Management Server | Microsoft Corporation |
| .CT5 | LexisNexis | Arquivos de dados | CaseMap Case Analysis Template | CaseMap | LexisNexis |
| .CT6 | LexisNexis | Arquivos de dados | CaseMap Case Analysis Template | CaseMap | LexisNexis |
| .CTB | Autodesk, Inc. | Arquivos de dados | AutoCAD Color-Based Plot Style File | Autodesk AutoCAD | Autodesk, Inc. |
| .CTD | NativeWinds LLC | Arquivos de dados | Compressed Tomahawk Document File | Tomahawk Gold | NativeWinds LLC |
| .CTE | Stefan Hagel | Arquivos de dados | Classical Text Editor Document File | Classical Text Editor | Stefan Hagel |
| .CTF | Interscape | Arquivos de dados | WhereIsIt Catalog File | WhereIsIt | Interscape |
| .CTI | Bitz & Pixelz | Arquivos de dados | Collectorz.com Template Info | Music Collector | Bitz & Pixelz |
| .CTK | Procedimientos-Uno, S.L. | Arquivos de dados | TeKton3D Project | TeKton3D | Procedimientos-Uno, S.L. |
| .CTL | Open Source | Arquivos de dados | StepMania SMZIP Package Description File | StepMania | Open Source |
| .CTM | LucasArts Entertainment Company, LLC | Arquivos de dados | Star Wars Republic Commando Map File | Star Wars Republic Commando | LucasArts Entertainment Company, LLC |
| .CTP | Cake Software Foundation | Arquivos de dados | CakePHP Template | Adobe Dreamweaver | Adobe Systems Incorporated |
| .CTRL | Oracle Corporation | Arquivos de dados | Oracle WebLogic Workshop Controls | WebLogic | Oracle Corporation |
| .CTT | Microsoft Corporation | Arquivos de dados | Messenger Contact List | Microsoft Notepad | Microsoft Corporation |
| .CTV | Swiss Academic Software | Arquivos de dados | Citavi Project | Citavi | Swiss Academic Software |
| .CTY | EA Maxis | Arquivos de dados | SimCity City File | Maxis SimCity 2000 | EA Maxis |
| .CTZ | Dextronet | Arquivos de dados | Custody Toolbox Compressed Backup File | Custody Toolbox | Dextronet |
| .CUB | Microsoft Corporation | Arquivos de dados | Analysis Services Cube File | Microsoft Excel | Microsoft Corporation |
| .CUBE | Open Source | Arquivos de dados | Gaussian Cube File | Avogadro | Open Source |
| .CUC | Naviter | Arquivos de dados | SeeYou Contest Document | SeeYou | Naviter |
| .CUL | CursorArts Company | Arquivos de dados | Windows Cursor Library | IconForge | CursorArts Company |
| .CURVE | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .CURXPTHEME | Stardock Corporation | Arquivos de dados | CursorXP Theme File | Stardock CursorFX | Stardock Corporation |
| .CUS | Autodesk, Inc. | Arquivos de dados | AutoCAD Custom Dictionary File | Microsoft Notepad | Microsoft Corporation |
| .CUT | Various Developers | Arquivos de dados | Dr. Halo Bitmap Image File | Lemkesoft GraphicConverter | Lemkesoft |
| .CV | Microsoft Corporation | Arquivos de dados | CodeView Data File | CodeView | Microsoft Corporation |
| .CVA | Hewlett-Packard | Arquivos de dados | HP SSM Information File | HP System Software Manager (SSM) | Hewlett-Packard |
| .CVD | invers Software | Arquivos de dados | Calamus Vector Image File | Calamus SL | invers Software |
| .CVJ | Vero Software | Arquivos de dados | Cabinet Vision Solid Job Document | Cabinet Vision Solid | Vero Software |
| .CVN | Sonic Solutions | Arquivos de dados | CineVision Encoding Session | Sonic CineVision | Sonic Solutions |
| .CVP | Symantec Corporation | Arquivos de dados | WinFax Cover Page | WinFax | Delrina |
| .CVS | Unknown Developer | Arquivos de dados | Comma Separated Values File | Microsoft Excel | Microsoft Corporation |
| .CVT | ACD Systems | Arquivos de dados | Canvas External Tool File | Canvas X | ACD Systems |
| .CW3 | Apple | Arquivos de dados | ClarisWorks Document | Apple Pages | Apple |
| .CW6 | Codeware Inc. | Arquivos de dados | COMPRESS Vessel Model File | COMPRESS | Codeware Inc. |
| .CWA | Horland Software | Arquivos de dados | Castelware Inventory Hardware/Software Audit File | CW Inventory | Horland Software |
| .CWK | Apple | Arquivos de dados | ClarisWorks Document | Apple Pages | Apple |
| .CWL | Open Source | Arquivos de dados | TeXstudio Completion Word List | TeXstudio | Open Source |
| .CWR | SAP | Arquivos de dados | Crystal Reports Report | Crystal Reports | SAP |
| .CWW | Variety Games | Arquivos de dados | Crossword Weaver Puzzle File | Crossword Weaver | Variety Games |
| .CXB | Custody X Change | Arquivos de dados | Custody X Change Data | Custody X Change | Custody X Change |
| .CXC | Custody X Change | Arquivos de dados | Custody X Change Data | Custody X Change | Custody X Change |
| .CXD | Hamamatsu Photonics K.K. | Arquivos de dados | SimplePCI Data Document | SimplePCI | Hamamatsu Photonics K.K. |
| .CXF | Google | Arquivos de dados | Google Picasa Collage File | Google Picasa | Google |
| .CXL | Pervasive Software | Arquivos de dados | Business Integrator Extract Schema | Pervasive Data Integrator | Pervasive Software |
| .CXO | Quantum CAD Ltd. | Arquivos de dados | CXInsight Export File | CXInsight | Quantum CAD Ltd. |
| .CXT | Omron Corporation | Arquivos de dados | CX-Programmer Project Text File | OMRON CX-One | Omron Corporation |
| .CYG | CyGem Ltd. | Arquivos de dados | Pollux Data File | CyGem Pollux | CyGem Ltd. |
| .CYL | Mike Carson | Arquivos de dados | Ribbons Cylinder File | Ribbons | Mike Carson |
| .CYO | Hot Neuron | Arquivos de dados | Clustify Output File | Clustify | Hot Neuron |
| .CYS | Hot Neuron | Arquivos de dados | Clustify Summary Statistics File | Clustify | Hot Neuron |
| .CYT | Crocodile Clips Ltd | Arquivos de dados | Yenka Simulation Data | Crocodile Clips Yenka | Crocodile Clips Ltd |
| .CZI | Carl Zeiss | Arquivos de dados | Carl Zeiss Image Data File | ImageJ | National Institutes of Health (NIH) |
| .CZP | Crick Software | Arquivos de dados | ClozePro Archive | ClozePro | Crick Software |
| .D02 | Cadence Design Systems | Arquivos de dados | MicroSim PCBoard NC Drill Data File | OrCAD PCB Designer | Cadence Design Systems |
| .D03 | Interscape | Arquivos de dados | Jydivide Split File | Jydivide | Interscape |
| .D04 | Cadence Design Systems | Arquivos de dados | MicroSim PCBoard NC Drill Data File | OrCAD PCB Designer | Cadence Design Systems |
| .D05 | Cadence Design Systems | Arquivos de dados | MicroSim PCBoard NC Drill Data File | OrCAD PCB Designer | Cadence Design Systems |
| .D06 | Cadence Design Systems | Arquivos de dados | MicroSim PCBoard NC Drill Data File | OrCAD PCB Designer | Cadence Design Systems |
| .D07 | Cadence Design Systems | Arquivos de dados | MicroSim PCBoard NC Drill Data File | OrCAD PCB Designer | Cadence Design Systems |
| .D10 | TaxAct | Arquivos de dados | Drake Software Data File | Drake Software | Drake Software |
| .D11 | NorthStar Solutions | Arquivos de dados | Macro Mania Data File | Macro Mania | NorthStar Solutions |
| .D3P | UnitedPrint.com | Arquivos de dados | DigitalPrintLab Data | DigitalPrintLab | UnitedPrint.com |
| .D4C | Open Source | Arquivos de dados | Dataphor Data File | Dataphor | Open Source |
| .D71 | Commodore International | Arquivos de dados | Commodore Emulator Data | VICE | Open Source |
| .D83 | GAEB | Arquivos de dados | GAEB 1990 Data | GAEB data exchange XML | GAEB |
| .DA2 | Microsoft Corporation | Arquivos de dados | Windows Dancer File | Windows Media Center | Microsoft Corporation |
| .DAB | Epigon Media Technologies | Arquivos de dados | Digital Audio Broadcasting Audio Data | DMB Player | Epigon Media Technologies |
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