Editing Atari DOS (section)

==={{anchor|2.0S|2.0D}}DOS 2.0===
:Also known as ''DISK OPERATING SYSTEM II VERSION 2.0S''
The second, more popular version of DOS from Atari was bundled with the 810 disk drives and some early [[Atari 1050]] disk drives. It is considered to be the [[lowest common denominator]] for Atari DOSes, as any Atari-compatible disk drive can read a disk formatted with ''DOS 2.0S''.

''DOS 2.0S'' consisted of <code>DOS.SYS</code> and <code>DUP.SYS</code>. <code>DOS.SYS</code> was loaded into memory, while <code>DUP.SYS</code> contained the disk utilities and was loaded only when the user exited to DOS.

In addition to bug fixes, ''DOS 2.0S'' featured improved <code>NOTE/POINT</code> support and the ability to automatically run an Atari [[executable]] file named <code>AUTORUN.SYS</code>. Since user memory was erased when <code>DUP.SYS</code> was loaded, an option to create a <code>MEM.SAV</code> file was added. This stored user memory in a temporary file (<code>MEM.SAV</code>) and restored it after <code>DUP.SYS</code> was unloaded. The previous menu option from ''DOS 1.0'', <code>N. DEFINE DEVICE</code>, was replaced with <code>N. CREATE MEM.SAV</code> in ''DOS 2.0S''.

Version ''2.0S'' was for [[#Disk formats|single-density]] disks, ''2.0D'' was for [[#Disk formats|double-density]] disks. 2.0D shipped with the ''[[Atari 815|815]]'' Dual Disk Drive, which was both expensive and incompatible with the standard 810, and thus sold only a small number; making DOS version ''2.0D'' rare and unusual.