DOS XL

DOS XL is a discontinued Disk Operating System (DOS) written by Paul Laughton, Mark Rose, Bill Wilkinson, and Mike Peters and published by Optimized Systems Software for the Atari 8-bit family of home computers. It was designed to be compatible with Atari DOS which came shipped with Atari, Inc.'s disk drives.
Description.
Features.
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 codice_1 files, DOS XL's batch features provided an auto-booting batch feature. Naming a batch file to codice_2 would have it execute batch commands on startup (same as OS/A+). Unfortunately, this feature wasn't compatible with some programs (e.g. AtariWriter).
Distribution.
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: Trak, Percom, Astra, Indus, Amdek, and Rana.
Commands.
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
Patch.
Version 2.30p was a newer version to 2.30 to fix two problems.
The patch for DOS XL 2.30 to make it a 2.30p:
100 READ CNT:IF CNT=0 THEN END
110 READ START
120 FOR ADDR=START TO START+CNT-1
130 READ BYTE:POKE ADDR,BYTE
135 NEXT ADDR
140 GOTO 100
150 DATA 3,5481,32,1,21
160 DATA 29,5377,141,217,22,169,16
170 DATA 141,23,22,169,23,141,24,22
180 DATA 169,49,141,30,22,169,64,141
190 DATA 12,0,169,21,141,13,0,96
200 DATA 1,7425,112,0
10 OPEN #1,12,0,"D:INIT.COM"
20 FOR I=1 TO 116 : GET #1,C : NEXT I
30 PUT #1,ASC("9") : CLOSE #1
Legacy.
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.