Atari disk operating systems generally support file specifications in the form
of a filename of 1 to 8 characters, with an optional filename extension of
zero to 3 characters.
Valid characters for use in filenames/filename extensions:
(varies somewhat by DOS version)
- The letters 'A' to 'Z'
- The digits '0' to '9'
(Many DOS versions do not permit filenames to start with a digit.)
- The underscore character ('_') (DOS XE,SpartaDOS,RealDOS)
- The "at" symbol ('@') (DOS XE)
Spaces and other characters are generally not permitted.
Filenames, including filename extensions, are generally arbitrary, but file
naming conventions can be helpful. The most common method is to reserve
specific extensions for certain types of files. The following list contains
some of the more commonly used extensions and their typical corresponding file
types.
Filenames reserved by some DOS versions for files to be automatically run at
system startup are listed here as well.
File formats are binary unless described below as "text" where:
- Binary format files are made up of a sequence of bytes of any value from
0-255.
- Text format files (technically, a special case of binary files) are
limited to printable/displayable alpha-numeric characters and symbols,
organized into lines.
.ACT Action! program source code
.ALF AlfCrunch archive file containing one or more compressed files
.AMP Antic Music Processor file
.AMS Advanced MusicSystem file or Advanced MusicSystem II file
.ARC Archive file containing one or more compressed files, compatible with
the multi-platform SEA ARC format. On the Atari, best supported by
SuperARC/SuperUnArc or the SpartaDOS X ARC external command.
.ASM Assembler Editor program source code, LISTed. ATASCII text.
.ASC ASCII text file
.ATA ATASCII text file
.BAS BASIC SAVEd program. Less common: .SAV
.BAT Batch file of DOS commands (DOS XE,SpartaDOS,RealDOS). ATASCII text.
- AUTOEXEC.BAT batch file runs at system boot
(DOS XE,SpartaDOS,RealDOS)
.BIN File transferred using CompuServe CIS 'A' Protocol. Fully supported on
the Atari by TSCOPE/MSCOPE/RSCOPE; also download support by Express! 3.x
(filenaming convention used on CompuServe before February 1987)
.BXL BASIC XL SAVEd program
.BXE BASIC XE SAVEd program
.CMD Batch file of DOS Commands (XDOS). ATASCII text.
.COM DOS external Command (DOS 2.5,DOS XE,SpartaDOS,RealDOS,XDOS)
.CTB Compiled Turbo-BASIC XL program
.DAT Data file (typically created/used by another program)
.DCM Disk Communicator 3.2 disk image file. Less common: .DSK or .DC3
.DOC Documentation text file (perhaps ASCII or ATASCII)
.DOS DOS system file (SpartaDOS,RealDOS)
.EXE Executable ('Load and Go') machine language (object code) program
.HLP Help text file (perhaps ASCII or ATASCII)
.LGO LOGO SAVEd workspace file. ATASCII text.
.LST LISTed BASIC program. ATASCII text. Less common: .LIS
.M65 MAC/65 SAVEd program source code
.MIC Micro-Painter picture file ("uncompressed"; 62 sectors under DOS 2.0S).
Format, minus color data, also supported by Illustrator versions using
the filename PICTURE and [Insert] to save file or [Clear] to load file.
.MUS Music Composer file
.OBJ Object code (machine language) file (not 'Load and Go')
.OBX Modern naming convention for an object code (machine language) file (not
'Load and Go'). Used to discourage modern computers from thinking that
Atari .OBJ files might be MS-DOS/MS-Windows object code files.
.PIC Micro Illustrator/KoalaPainter/AtariArtist "compressed" picture
.PLT PILOT SAVEd program. ATASCII text.
.PRN Text file formatted for copying to Printer (perhaps ASCII)
.SAV File named MEM.SAV may be employed by DOS to preserve the contents of
memory to disk when DUP.SYS (DOS 2.0,DOS 2.5) or KCP.SYS (DOS 3) is
loaded into memory.
.SCP SpartaDOS SCOPY disk image file. Used with SCOPY, an external command
distributed with SpartaDOS 3.2.
.SFX Self-Extracting archive file. Created with the CTH SFX program.
.SYS DOS System file or driver
- AUTO.SYS can be used to automatically poke data in RAM locations on
system startup (DOS I)
- AUTORUN.SYS binary file is launched on system boot
(DOS 2.0,DOS 3,DOS 2.5,RealDOS,XDOS)
- AUTORUN.SYS batch file of DOS commands runs at system boot (XDOS)
.TUR Turbo-BASIC XL SAVEd program. Less common: .TBS
.TXT Text file (perhaps ATASCII or ASCII)
.UTL A DOS external utility program (DOS 3)
.XEX Modern naming convention for an executable ('Load and Go') machine
language (object code) program. Used to discourage modern computers
from thinking that Atari .EXE files might be MS-DOS/MS-Windows
executable programs.
.XMO Binary file, uploaded/download using XMODEM file transfer protocol
(filenaming convention used on CompuServe before February 1987)
Additional file extensions associated with Atari picture formats are listed at
the website for RECOIL (Retro Computer Image Library), a viewer of pictures in
native formats of the Atari 8-bit (and other platforms) for modern computers:
http://recoil.sourceforge.net/
Additional file extensions associated with Atari music formats are listed at
the website for ASAP (Another Slight Atari Player), a player of Atari 8-bit
music for modern computers: http://asap.sourceforge.net/
File extensions associated with Atari disk image, cassette image, or cartridge
ROM formats normally used with Atari emulators, rather than on the Atari
itself, are described elsewhere in this FAQ list.
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