| fca | Omnis Web Client Form Cache |
| fcat | Fact200 Categories Data |
| fcc | SiteMinder Forms Credential Collector Data |
| fcdot | ABBYY FlexiCapture Engine Document Definition |
| fcg | GAUSS Engine Compiled Gauss Data |
| fch | Gaussian Formatted Checkpoint File |
| 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 |
| fcpcache | Final Cut Pro Cache Data |
| fcpevent | Final Cut Pro Event Data |
| fcs | Canon ZoomBrowser EX Data |
| fcs | Flow Cytometry Standard Data |
| fcst | Delft-FEWS Forecast Data |
| fct | FolderClone Task List |
| fcz | Poser Compressed Face Data |
| fd | STK Facility Database Main File |
| fdat | Fiasco Database Data File |
| fdata | NONMEM Data |
| fdc | Autodesk AutoCAD Fields Description |
| fde | AFP Form Definition |
| fdf | Format Description File |
| fdf | Origin Fitting Function Definition File |
| fdk | Fluentizer Dictionary Data |
| fdm | SIPINA FDM Data |
| fdn | MODFLOW Drawdown Data |
| fdo | ModelSim Script |
| fdp | Viamichelin Map File |
| fdp | Epson PhotoQuicker Frame |
| fdt | Visilogic Utilities Full Data Table |
| fdt | Lucene Field Data |
| fdx | Food Data Exchange File |
| fdx | Lucene Field Index |