Almost All File Formats and their Meanings

R
R Pegasus Mail resource file
RA Real Audio sound
RAM Real Audio sound
RAS Sun Raster Images bitmap
RAW Raw File Format (bitmap)
RC Microsoft Visual C++ Resource Script
REC Recorder macro
REG Registration file
RES Microsoft Visual C++ Resource
RFT RFT-DCA
RLE Run-Length Encoded bitmap
RM Real Audio video file
RMI MIDI music
ROV Rescue Rover data file
RPT Microsoft Visual Basic Crystal Reports file
RTF Rich Text Format document
RTM Real Tracker music module (MOD) file