.??_  Files ending in "_" are often compressed install files of the same
          name (e.g., .EX_ expands to .EXE, .DL_ expands to .DLL, etc.)
  .R    Pegasus Mail Resource File
        Rebol Script
        Progress Compiled Program File
        Ratfor FORTRAN Preprocessor File  [FORTRAN]
  .R??  RAR Compressed File (?? can be 00 to 99)
  .R1A  Yamaha RM1x Dance-Music Workstation
  .R2A  Yamaha RS7000 Music Production Studio Sequencer
  .R2D  RISA-2D Simple Analysis & Design
  .R2K  Repertoire 2000 Music Database
  .R2P  Yamaha RS7000 Music Production Studio Sequencer
  .R33  Train Simulator Game File
  .R3A  Yamaha RS7000 Music Production Studio Sequencer
  .R3D  RISA-3D 3D Analysis & Design
  .R3P  Yamaha RS7000 Music Production Studio Sequencer
  .R64  Top Secret Crypto File
  .R8   RAW Graphic File
        Flight Simulator Texture File
  .R8L  LaserJet Landscape Font
  .R8P  LaserJet Portrait Font
  .RA   RealMedia File  [IrfanView]
  .RAD  Radiance Scene Description Format  [XnView]
  .RAM  RealMedia Metafile
  .RAN  Dexterpen File (Parametric 2D design and calculation)
  .RAP  Rapanalyst File (Rapid Application Predictive Technology Organization Resource)
        Rapidocs Document
  .RAR  RAR Compressed Archive
        Java JCA Resource Adapter Module
  .RAS  Sun Raster Graphic  [XnView] [IrfanView]
        Cals Raster File [SwiftView]
        Max Payne Data File
        Sky Subtracted Data
  .RAST  Sun Raster Graphic  [XnView]
  .RAT  Rating System File
        Rats Data
        Nimbus 7 SAMS Data File (radiance data)
  .RAW  RAW RGB 24-bit Graphic  [XnView]
        Raw Signed PCM Data
        Sentry 2020 Encryption File
        VitaGraph File (medical testing related)
        Nimbus 7 SAMS Data File (radiance data)
        HSI Raw File  [XnView]
        Spectrum Raw Memory Dump
        V41/eV41 Program Files
  .RAX  Image File
  .RB   RocketEdition File
        Ruby Interpreter Program
  .RB1  R:Base Data File
  .RB2  R:Base Data File
  .RB3  R:Base Data File
  .RBB  Top Secret Crypto File
  .RBF  R:Base Data File
        Oracle Backup File
        MS Rollback File (backup of existing file stored in hidden config.msi directory)
  .RBH  RoboHelp Configuration
  .RBM  Propellerhead ReBirth Modulation v2.0
        Rail Baron Player Map
  .RBN  Richard's Bridge Notation
        Real Sound File
  .RBO  Sometimes associated with the Magistr.B Worm [Worm Info]
  .RBPM  POrtable Bitmap  [XnView]
  .RBS  Propellerhead Software ReBirth Song
        Rutherford Backscattering Spectroscopy Analysis Package (RUMP)
        MS Rollback Script (see .RBF)
  .RBX  XStream Multimedia Simulation Format
  .RBZ  Rail Baron Player Saved Game
  .RC   Borland C++ Resource Compiler Script File
        Emacs Configuration
  .RC2  ReCycle v.2 Audio Loop
  .RCD  PC Anywhere Recorded Session File
  .RCG  Netscape Newsgroup File
  .RCH  SWAT Reach Output File (river basin scale model)
  .RCM  Logos Library System 2.x Verse Map
  .RCP  Recomposer's MIDI Sequencer Music File
  .RCS  Colin McRae Rally Save Game File (unverified)
  .RCX  Lego Mindstorms Robotics Invention System
  .RCY  ReCycled Audio Loop
  .RD1  Descent1 Registered Level File
        DATAIR Retirement Document System Data File
  .RD2  DATAIR Retirement Document System Custom Text File
  .RD3  Ray Dream Designer Graphics
        CorelDream 3D
  .RD4  Ray Dream Designer Graphics
  .RD5  Ray Dream Designer Graphics
  .RDA  Oracle Storage Area File
  .RDB  TrueVector Rules Database
        ZoneAlarm Rules Database  (IAMDB.RDB file)
        Gear CD Suite File
        Oracle Database Root File
  .RDF  Resource Description Framework File
        Geoworks UI Compiler Source Code
        Chromeleon Report Definition
        Workshare Synergy Collaboration Response File
        Burli Newsroom System File
        Oracle Report Binary Source
        Rate Description File (BLDRATE.EXE output)
  .RDI  Device-independent Bitmap
  .RDL  Descent Registered Level
        RadioDestiny Radio Stream
        Symbian Recogniser Library (allows OS to recognize document formats)
  .RDP  Remote Desktop Connection
  .RDS  Ray Dream Studio File
  .RDT  RDT Tracking File (capture design process and manage the system requirements)
  .RDX  Reflex Data File
  .REC  Sprint Record File
        EpiInfo Data
        Windows Recorder Macro
        RapidComm Voice File
  .RED  Calrion Modula-2 Path Data
  .REF  Cross Reference
  .REG  Registration Data (various)
  .REGET  ReGet Deluxe Downloader
  .REM  Annotation (remark)
  .REP  Text Document
        Report File (various)
        Blizzard Entertainment Replay File
        Qwk Reader Reply
  .REQ  Request
  .RES  Resource File (various programs)
        Championship Bass Archive  [Dragon UnPACKer]
        Evil Islands Archive  [Dragon UnPACKer]
        Half Life Game Map [Maps] [Viewers]
  .RESX  MS .NET XML Resource Template
  .REV  Geoworks Revision File
        Workshare Synergy File
        WinRAR Recovery Volume File
  .REX  REXX Program File
        Oracle Report Definition
        ReCycled Audio Loop Export File
        4D Database Windows Client Local File
  .REZ  Resource File
        Aliens and Predator 2 Game File
        Blood 2 Archive  [Dragon UnPACKer]
        No One Lives for Ever Archive  [Dragon UnPACKer]
        Sanity: Aiken's Artifact Archive  [Dragon UnPACKer]
        Shogo Archive  [Dragon UnPACKer]
  .RF   Sun Raster Graphic
        RealFlash Clip
  .RF?  SmartWare Compiled Project File (requires login)
  .RFB  RoboForm
  .RFD  RecogniFORM Form Definition
        Emperor: Battle for Dune Archive  [Dragon UnPACKer]
  .RFF  Maggi Graphic File
  .RFG  RFG Integrator System Database
  .RFH  RFG Integrator Householding Database
        Maxagrid CTM Refresh File (text format)
  .RFL  RISAFloor Analysis & Design
        Reason Sound File
        Guardian Database Roll-forward File
  .RFP  AI RoboForm Passcard Database
  .RFT  IBM DisplayWrite Revisable Format Text
        AI RoboForm Form Database
  .RGB  Q0 Graphic  [XnView]
        Silicon Graphics RGB  [XnView]
  .RGBA  Silicon Graphics RGB  [XnView]
  .RGI  RealArcade Game Installer (not secured)
  .RGL  Scarlett Expert System Compiler Rules File (Scarlett is not presently available)
  .RGN  Championship Manager Game File
  .RGP  RealArcade Game Package
  .RGS  RealArcade Game Installer (secured)
  .RGX  ReaGeniX Code Generator Symbol Table
  .RH   Borland C++ Resource Header File
  .RI   Lotus File
  .RIA  Alpharel Group IV Raster Graphics File
  .RIB  3D Reality Renderman Format Graphics
  .RIC  Ricoh FAX Graphic File
  .RIF  Fractal Painter Bitmap
  .RIN  RappInfo PostScript Converter Configuration File
  .RIP  Remote Imaging Protocol
  .RIX  ColorRIX VGA Paint File  [XnView]
        RIX Virtual Screen
  .RL   The 7th Guest Archive  [Dragon UnPACKer]
  .RL1  Descent1 Registered Level File
  .RL2  Descent2 Registered Level
  .RL4  Bitmap Graphics
  .RL8  Bitmap Graphics
  .RLA  Advanced Visualizer File
        Wavefront Raster Image
  .RLB  Harvard Graphic File (Harvard Graphics taken over by Serif)
  .RLC  Image Systems CAD Overlay (RLC2 Graphic)  [XnView]
        Scanner One-bit/pixel Grahpic Output
  .RLE  Graphic (Run Length Encoded)  [XnView] [IrfanView]
        Utah Raster Image  [XnView]
  .RLZ  Realizer Source Code
  .RM   RealMedia File
  .RMD  RegMaid Document
  .RMF  Rich Map Format (3D Games)
        Acrobat File
  .RMI  MIDI File  [IrfanView]
  .RMJ  Real Jukebox File
  .RMK  Clipper RMake Make File
  .RML  Redline Markup Language File (XML-based exchange of design markup and redline information)
  .RMM  RealPlayer File
  .RMR  Resume Maker File
  .RMS  AutoCAD Data File for Boss RMS (River Modelling System)
        Secure RealMedia File
  .RMX  RealJukeBox MP3 File
  .RN   Nota Bene XPL Program
  .RND  AutoCAD Rendering Slide
        AutoShade Format
  .RNG  Nokia Ringtone File
        Top Secret Crypto File
  .RNL  GTX Runlength Raster Graphics
  .RNO  VAX Runoff File
  .RNX  RealPlayer File
  .ROI  Actuate ReportBlast File
  .ROL  Adlib Music File
  .ROM  Nintento 64® Emulation ROM Image
        (actually most any emulator or BIOS flasher)
        MZ700 Emulator (MZ700.ROM)
  .ROQ  Medal of Honor - Allied Assualt
  .ROV  Rescue Rover Data
  .ROX  Actuate ReportBlast File
  .RP   RealPix Clip
        Rainbow Painter  [XnView]
  .RP?  RescuePro Physician Invoice File (? can be 0-9)
  .RPB  Automotive Diagnostic File
  .RPBM  Portable Image  [XnView]
  .RPC  Rich Photorealistic Content (ArchVision, Inc.)  [Info]
  .RPD  Rapidfile Database
        RPV Printing System File
  .RPGM  Portable Greyscale  [XnView]
  .RPIN  Adobe InDesign Import/Export Filter
  .RPJ  Relex (Reliability Analysis Software)
  .RPK  Rippack File
  .RPL  Replica Text File
  .RPM  RedHat Package Manager (Linux Library)
        RealMedia Player File
        RunPaint Multicolor Graphic  [XnView]
  .RPNM  Portable Image  [XnView]
  .RPPM  Portable Image  [XnView]
  .RPS  Propellerhead Software Reason Song
  .RPT  Report (various)
  .RPV  Real Player Visualization File (animated effects to beat of music)
        RPV Printing System File
        Rebel Poker Player File (Note: Strip poker with nude graphics)
  .RPW  RPWiz Project (slide show development)
  .RPY  Star Wars - Tie Fighter Media
        Grand Prix Legends Racing Simulation Game File
  .RQY  MS Excel OLE DB Query File [Buy Office XP at Shop.Microsoft]
  .RR   Railroad Tycoon
  .RRD  ERDAS Imagine File (remote sensing)
  .RRS  Road Rash Save File
  .RS   Amiga Reassembler Resource Data File
        EROSION 3D Event File [Format (pdf)]
        Sun Raster Graphic  [XnView]
  .RS_  Macintosh File Resource Fork
  .RSB  Rogue Spear Bitmap
        Red Storm Image Format  [XnView]
  .RSC  Resource File
        SymbianOS Application Resource File (application resources)
  .RSF  Mediafour MacDrive Macintosh Resource Fork
  .RSL  PC Tools Resources Library
        Borland's Paradox 7 Report
        Adobe Pagemaker File
  .RSM  RuneSword II Game
        Resume (often an MS Word file)
        WinWay Deluxe Resume File
  .RSML  Real Player File
  .RSN  Propellerhead Reason Audio File
  .RSP  Responce Text File
        MS ODBC Driver Configuration File (Installation direcives used setting up MS Universal Data Access services)
        Rockwell Software Logix 5 File
        Workshare Synergy Response File
        MDaemon File
  .RSR  4D Database Resource Fork File (.4D? for data fork)
  .RSS  Rockwell Logix 500 SLC-5 Software
  .RST  ANSYS Results
  .RT   Real Media File
  .RTA  RoboHelp Configuration
  .RTF  Rich Text Format File (also used as Windows Help file script)
  .RTH  ANSYS Results
  .RTK  RoboHelp Configuration
  .RTL  Text File
        NU 7.0 Runtime Library
  .RTM  Real Tracker Music Module
  .RTP  TurboTax Update File
        RTPatch Update Package
        Gerber Sign-making Software File
  .RTS  RoboHelp Configuration
        RealAudio RTSL Document
        Realizer Runtime Library
  .RTX  Reliacast Audience Manager Turnstile
        Mobile Phone Ringtone (extended ringtone format)
  .RUJ  Oracle Recovery-Unit Journal
  .RUL  InstallShield
  .RUN  PC Tools Script Tools Program
  .RV   RealVideo Clip
  .RVG  Revit External Group File
  .RVI  Revenant Archive  [Dragon UnPACKer]
  .RVM  Revenant Archive  [Dragon UnPACKer]
  .RVN  Riven Saved Game
  .RVP  Microsoft Scan Configuration File
        C|Net CatchUp File Mime Type: application/x-mss-scancfg
  .RVS  Revenant Archive  [Dragon UnPACKer]
  .RVT  Apache Rivet Tcl File
        IEX Workforce Management Report (text file)
        Incite Media Assistant File
        Revit Design Setup File
        VersaPro Reference View Table
  .RVW  Review (may just be text file)
  .RWD  Symphonie Raw Wind Data
  .RWG  Random Word Generator
  .RWP  IBM Configurator Report (if you don't have the program ask the sender to export to .RTF for you)
  .RWS  Borland C++ Resource Workshop Data File
  .RWX  RenderWare Script
  .RWZ  MS Outlook Rules Wizard File
  .RX   Reflex Database Driver
        EARS Component File (EARS = UK Liberal Democrats Election Agents Record System) [Filename starts with E]
  .RXC  WRQ Reflection X Connection
  .RXD  Reflex Database
  .RXF  Recipe Exchange Format (Resort Software format for chef/food & beverage manager data exchange)
  .RXH  Reflex Database Help File
  .RXN  MDL RxnFile (MIME type chemical/x-mdl-rxnfile)
  .RXR  Reflex Database Report
  .RXS  Reflex Database Screen Driver