Screenshot of DOS XL
Original author(s) Paul Laughton, Mark Rose, Bill Wilkinson and Mike Peters
Developer(s) Optimized Systems Software
Discontinued 2.30 / 1984 (1984)
Platform Atari 400/800/XL/XE
Type Atari DOS
License Copyright © 1994 FTe Proprietary software

DOS XL was a Disk Operating System (DOS) written by Paul Laughton, Mark Rose, Bill Wilkinson and Mike Peters and produced by Optimized Systems Software (OSS) for Atari 8-bit microcomputers. It was designed to be compatible with Atari DOS which came shipped with Atari's disk-drives.




A direct descendant of OS/A+, DOS XL provided additional features to Atari's equipped with floppy disk drives. These included single and double density support, a command-line mode (called the command processor or CP), a menu mode (an executable loaded in memory), batch file support, and support for XL extended memory and OSS SuperCartridge banked memory. Later versions included Axlon RamDisk support, Mosaic RamDisk support, BIT-3 support and BUG/65.

In addition to supporting auto-booting AUTORUN.SYS files, DOS XL's batch features provided an auto-booting batch feature. Naming a batch file to STARTUP.EXC would have it execute batch commands on startup (same as OS/A+). Unfortunately, this feature wasn't compatible with some programs (e.g. AtariWriter).


DOS XL was distributed on a flippy disk. One side had the single-density version, the other had the double-density version. As more features and add-ons were included, these were placed on the double-density side only due to lack of disk space.

The manual for DOS XL was a subset of OS/A+. OSS considered the manual an "addendum" to OS/A+. Over 150+ pages, it was bound at the spine, not in loose-leaf form like the OS/A+ manual.

DOS XL came in two versions, 2.20 and 2.30 (2.20 users had to pay $20 to upgrade to 2.30). The last version was 2.30P. DOS XL originally sold for $30, but the price later increased to $39.

File writing verify was turned off in DOS XL. This was due to OSS's own experience that resulted in faster writes with virtually no risk of errors. The command file VERIFY.COM was included to reenable writes with verify. Atari DOS 2.0S by default verified file writes to disk.

Several Disk Drive manufacturers shipped DOS XL with their drives, including Trak, Percom, Astra, Indus, Amdek and Rana.


Menu Commands

 C - Copy Files            P - Protect Files
 D - Duplicate Disk        Q - Quit to DOS XL
 E - Erase Files           R - Rename File
 F - Files on Disk         S - Save Binary
 G - Go to Address         T - To Cartridge
 I - Initialize Disk       U - Unprotect Files
 L - Load Binary           X - Xtended Command

Intrinsic Commands

 @ - Begins execution of a batch file
 CAR - Runs Cartridge
 Dn: - Changes default drive
 DIR - Directory
 END - Tells DOS XL to stop batch execution (used in a batch file)
 ERA - Erase file(s)
 LOA - Load file(s) in memory
 NOS - NO Screen. Turns off command echo to screen
 PRO - Protect. Enables write-protect on file(s)
 REM - REMark. Used for user remarks in batch files
 REN - REName. Renames file(s)
 RUN - Jumps to run address
 SAV - Saves a portion of memory to disk
 SCR - Enables commands to be echoed to screen (for batch files)
 TYP - Displays ASCII or ATASCII text files to screen
 UNP - Turns off write-protect on file(s)

Extrinsic Commands

 C65         DUPDBL       MENU        VERIFY
 CONFIG      INIT         RS232
 COPY        INITDBL      RS232FIX
 DO          MAC65        SDCOPY

BASIC Extended Commands

 CLOSE       NOTE          PROTECT   (XIO 35)
 ENTER       OPEN          UNPROTECT (XIO 36)
 GET         POINT         RENAME    (XIO 32)     
 INPUT       PRINT         ERASE     (XIO 33)      
 LIST        PUT
 LOAD        SAVE


Version 2.30P was a newer version to 2.30 to fix two problems.

  • In previous versions of DOS XL, if you initialized a disk from the menu, the disk would not boot unless the file MENU.COM was on the disk. To alleviate this problem, type Q to quit the menu. Then type INIT or INITDBL from the command processor. Note: everything on the menu can be done manually from the command processor.
  • If you have a multidrive system and you initialized a disk in a drive other than one, when booted, the disk will always come up with the number of the drive on which it was initialized. To prevent this problem, use D1: as the destination drive.

The patch for DOS XL 2.30 to make it a 2.30P:

  10 XIO 36,#1,0,0,"D:DOS.SYS" : REM unprotect file
  20 OPEN #1,12,0,"D:DOS.SYS"
  80 GOTO 30
  200 DATA 3,5481,32,1,21
  210 DATA 27,5377,141,217,22,169,16
  220 DATA 141,23,22,,169,23,141,24,22
  230 DATA 169,49,141,30,22,169,64,133
  240 DATA 12, 169,21,133,13,96
  250 DATA 0
  300 CLOSE #1
  310 END


Plans for DOS XL 4 were scrapped due to low demand and competition. OSS reissued OS/A+ 4.1, mainly for double-sided support.

DOS XL, along with other OSS products, became part of ICD's catalog of Atari products in January 1988. However, DOS XL was dropped in favor of ICD's SpartaDOS.


  • Inside Atari DOS Introduction by Bill Wilkinson, 1982
  • A User's Guide and Reference Manual for DOS XL 2.30, 1983
  • OSS Newsletter - Spring 1984
  • OSS Newsletter - October 1984

External links

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