| fc3 | FCEUX Saved State |
| fca | Omnis Web Client Form Cache |
| fcat | Fact200 Categories Data |
| fcc | SiteMinder Forms Credential Collector Data |
| fcdot | ABBYY FlexiCapture Engine Document Definition |
| fcf | XtalView Xfit Phase Data |
| fcg | GAUSS Engine Compiled Gauss Data |
| fch | Gaussian Formatted Checkpoint File |
| fchc | Fetch Cache Data |
| fchk | Gaussian Formatted Checkpoint File |
| fci | Erosion 3D Inflow Table |
| fci | Fiery Clone Tool Image |
| fciv | Microsoft File Checksum Integrity Verifier Data |
| fcm | Brother ScanNCut Data |
| fcod | Adobe PageMaker Filter Data |
| fcp | FLAMES Checkpoint Restart Data |
| fcpcache | Final Cut Pro Cache Data |
| fcpevent | Final Cut Pro Event Data |
| fcpxdest | Final Cut Pro Share Destination Data |
| fcs | Canon ZoomBrowser EX Data |
| fcs | Flow Cytometry Standard Data |
| fcst | Delft-FEWS Forecast Data |
| fct | FolderClone Task List |
| fcxr | FileCapsule Deluxe Data |
| fcxu | FileCapsule Deluxe Data |
| fcz | Poser Compressed Face Data |
| fd | STK Facility Database Main File |
| fd1 | Windows Live Photo Gallery Thumbnail Database |
| fdat | Fiasco Database Data File |
| fdata | NONMEM Data |
| fdb | Firebird SQL Database |
| fdb | FormTool Pro Form Data |
| fdc | Autodesk AutoCAD Fields Description |
| fdd | FlexiDATA Database |
| fde | AFP Form Definition |