| cgc | Compressed Gamecube Disk Image |
| cgd | CricketGraph Data |
| cgh | Clinical Genomics Data |
| cgk | BlueSoleil Driver Data |
| cgm | Altair FEKO Matrix Equation Data |
| cgn | PoldatDB Data |
| cgns | CFD General Notation System Data |
| cgp | PixelCryptor Encrypted File |
| cgrp | Avid Pro Tools Clip Group File |
| cgt | SmartCAM Code Generation Template |
| cgx | Autodesk Land Desktop Label Style |
| ch10 | IRIG 106 Original Recording Data |
| ch5 | VisIt CH5 Data |
| ch6 | ZX-Paintbrush Character Data |
| ch8 | CHIP-8 Program |
| ch8 | ZX-Paintbrush Character Data |
| cha | Adobe Photoshop Channel Settings |
| changedb | SQLite Changes Data |
| chapters | ChapterGrabber Chapters Data |
| char | Nintendo DS Character Tile Data |
| charmm | CHARMM Data |
| charset | Mac OS X Character Set Data |
| chatlog | Adium Chat Log |
| chb | CHMReader.NET Internal Data |
| chb | OLE DB Checkbook Data |
| chc | HCFR Colorimeter Data |
| chck | Microsoft Exchange Database Check Data |
| check | CASTEP Check Binary |
| chem | TI bqEASY Chemistry Data |
| chg | Quicken Online Data |
| chg | Windows Netlogon ChangeLog |
| chj | IBM SPSS Interview Cache |
| chk | DB/TextWorks Check Textbase Problem Report |
| chk | Epidata Defined Checks |
| chk | Gaussian Checkpoint File |