| .C V | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .C#= | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .C0 | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .C1A | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .C20 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .C2I | Unknown Developer | Ficheiros de Sistema | Driver File | Unknown Software | Unknown Developer |
| .C3B | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .C61 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .C9 | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .CAKEWALKWI | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CALC | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .CALENDAR19 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CAMERA | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CAO | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CARAMBA | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CASECONVER | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CATANALYSI | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CATDRAWIN | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CATMATERIA | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CBI | IBM | Ficheiros de Dados | IBM System/360 Column Binary Formatted File | Unknown Software | Unknown Developer |
| .CBIN | Unknown Developer | Uncommon Files | CACTVS Chemical Binary File | Unknown Software | Unknown Developer |
| .CC | Don Ho | Ficheiros de Desenvolvedor | C/C++ Source Code File | Unknown Software | Unknown Developer |
| .CCA | IBM | Ficheiros de Dados | Cc:Mail Archive File | Unknown Software | Unknown Developer |
| .CCH | Microsoft Corporation | Uncommon Files | .NET Security Resolution Cache File | Unknown Software | Unknown Developer |
| .CC_ | Unknown Developer | Ficheiros de Áudio | Audio Utility Midimach Compressed File | Unknown Software | Unknown Developer |
| .CDEVSAMPLE | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CDMIA | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CDMIC | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CDMID | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CDMIO | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CDMIQ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CED | JVCKenwood Group | Ficheiros de Vídeo | JVC Camera Video Data File | Unknown Software | Unknown Developer |
| .CEE | Unknown Developer | Ficheiros GIS | Compressed GPS Ephemeris Data | Unknown Software | Unknown Developer |
| .CEG | Unknown Developer | Ficheiros Gráficos | Tempra Show Bitmap Graphic File | Unknown Software | Unknown Developer |
| .CEN | European Committee for Standardization | Ficheiros de Dados | CEN EN 13032 Photometric Data | Unknown Software | Unknown Developer |
| .CES | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .CGB | Unknown Developer | Ficheiros de Dados | Gameboy Color Data | Unknown Software | Unknown Developer |
| .CHANGELOG | Unknown Developer | Uncommon Files | Project Log Or Record File | Unknown Software | Unknown Developer |
| .CHB | Microsoft Corporation | Ficheiros de Desenvolvedor | OLE-DB Checkbook File | Unknown Software | Unknown Developer |
| .CHXX | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CHZ | Unknown Developer | Ficheiros Compactados | ChArc Compressed File Archive | Unknown Software | Unknown Developer |
| .CIB | DIAL | Ficheiros CAD | DIALux Luminaire Data | Unknown Software | Unknown Developer |
| .CKN | Disk Doctor Labs Inc. | Ficheiros de Dados | Disk Doctors License Log | Unknown Software | Unknown Developer |
| .CLM | YMAX | Ficheiros de Dados | MagicJack Call Log File | Unknown Software | Unknown Developer |
| .CLOG | SpreadMaster | Ficheiros de Dados | SpreadMaster Client Log File | Unknown Software | Unknown Developer |
| .CM | Rockstar Games | Ficheiros de Jogo | CLEO Custom Mission | Unknown Software | Unknown Developer |
| .CMGZ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CNDF | Unknown Developer | Ficheiros de Dados | Technomate CNDF Channel Editor Compressed Channel File | Unknown Software | Unknown Developer |
| .CO3 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .COCO | Unknown Developer | Uncommon Files | Unknown Apple II Data File | Unknown Software | Unknown Developer |
| .COM1476662 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .COMICSCART | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .COMMANDLIN | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .COMPLICATI | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .COMPRESSIO | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CONFIDENTI | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CONFIGDBLI | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CONTENTSON | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CONTROLPAN | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CONVERSION | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CONVERTER | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .COOKIES | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .COP | Cisco Systems | Ficheiros de Configurações | CISCO Options Package Settings | Unknown Software | Unknown Developer |
| .CORE | Unknown Developer | Ficheiros de Imagem 3D | Core Bitmap Image File | Unknown Software | Unknown Developer |
| .CORELPROJE | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CORES | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CORRECT | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .CORRECTED | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CP2 | Unknown Developer | Ficheiros de Layout de Página | Compel V2 Presentation | Unknown Software | Unknown Developer |
| .CPH_9FA6FA | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CPZ | Terry A. Davis | Ficheiros de Desenvolvedor | LoseThos C+ Source File | Unknown Software | Unknown Developer |
| .CQ1 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CRA | Unknown Developer | Uncommon Files | Advanced Crack File | Unknown Software | Unknown Developer |
| .CRACK | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .CRACKZBYMA | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CRN | Unknown Developer | Ficheiros de Dados | Tree Ring Data File | Unknown Software | Unknown Developer |
| .CRUNCH | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .CRYPTO | Unknown Developer | Uncommon Files | Scarab/CryptoKill Ransomware Virus | Unknown Software | Unknown Developer |
| .CRYPTONOTE | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CRYSIS | Unknown Developer | Ficheiros Encriptados | CrySiS Ransomware Encrypted File | Unknown Software | Unknown Developer |
| .CRYSTALHAM | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CS_ | Unknown Developer | Ficheiros de Dados | Creativ Compressed Sb16 Sbide File | Unknown Software | Unknown Developer |
| .CTG | Canon Inc. | Uncommon Files | Canon Digital Camera Catalog File | Unknown Software | Unknown Developer |
| .CUID | Unknown Developer | Uncommon Files | Baidu.cuid Data | Unknown Software | Unknown Developer |
| .CUREXSCHEM | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CURVE | Apple | Ficheiros de Dados | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .CVE | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CXM | Unknown Developer | Ficheiros de Imagem 3D | QuadColor Color Correction Master Data | Unknown Software | Unknown Developer |
| .CX_ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .CY | Unknown Developer | Uncommon Files | CCS-lib.2 JPEG-v4 File | Unknown Software | Unknown Developer |
| .CYN | Unknown Developer | Uncommon Files | Cynex Root55 Program Extension File | Unknown Software | Unknown Developer |
| .CZK | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
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