| Abbreviation | Definition |
|---|---|
| RDB | Relational Data Base |
| RDDF | Route Description Data File |
| RDEF | Geoworks UI resource file (old) |
| RDF | Geoworks UI Compiler, Compiled UIC source code |
| RDF | Report Definition File |
| RDI | RIFF RDIB Device-independent bitmap file |
| RDX | Reflex Datafile |
| REC | ARCSERVE Archivation Protocol |
| REC | EpiInfo Datafile |
| REC | Record (Sprint) |
| REC | Windows Recorder Macro |
| RED | Clarion Modula-2 Path information |
| REF | Cross Reference |
| REG | Registration information or key |
| REM | Remarks |
| REP | Reply file ( Qwk Reader) |
| REP | Report file |
| REQ | Request |
| RES | Compiled resource (MS C/C++ - Borland C++) |
| RES | Resource |