Editing OS/2 (section)

====OS/2 2.1 (1993){{anchor|2.1}}====
OS/2 2.1 was released in 1993. This version of OS/2 achieved compatibility with Windows 3.0 (and later Windows 3.1) by adapting Windows user-mode code components to run inside a [[virtual DOS machine]] (VDM). Originally, a nearly complete version of Windows code was included with OS/2 itself: Windows 3.0 in OS/2 2.0, and Windows 3.1 in OS/2 2.1. Later, IBM developed versions of OS/2 that would use whatever Windows version the user had installed previously, patching it on the fly, and sparing the cost of an additional Windows license.<ref>{{cite web |title=Team OS/2 Frequently Asked Questions |author=Christian Alice Scarborough |date=15 September 1998 |url=http://www.faqs.org/faqs/Team-OS2-FAQ/}}</ref> It could either run full-screen, using its own set of video drivers, or "seamlessly," where Windows programs would appear directly on the OS/2 desktop. The process containing Windows was given fairly extensive access to hardware, especially video, and the result was that switching between a full-screen WinOS/2 session and the Workplace Shell could occasionally cause issues.<ref>{{cite web |title=OS/2 Games Setting Archive |work=Game Zero magazine |date=6 March 1995 |url=http://www.gamezero.com/team-0/pc_games/os2.html |access-date=9 June 2006 |archive-url=https://web.archive.org/web/20060614014635/http://www.gamezero.com/team-0/pc_games/os2.html |archive-date=14 June 2006 |url-status=dead }}</ref>

Because OS/2 only runs the user-mode system components of Windows, it is incompatible with Windows device drivers ([[VxD]]s) and applications that require them.

Multiple Windows applications run by default in a single Windows session – multitasking cooperatively and without memory protection – just as they would under native Windows 3.x. However, to achieve true isolation between Windows 3.x programs, OS/2 can also run multiple copies of Windows in parallel, with each copy residing in a separate VDM. The user can then optionally place each program either in its own Windows session – with preemptive multitasking and full memory protection ''between'' sessions, though not ''within'' them – or allow some applications to run together cooperatively in a shared Windows session while isolating other applications in one or more separate Windows sessions. At the cost of additional hardware resources, this approach can protect each program in any given Windows session (and each instance of Windows itself) from every other program running in any ''separate'' Windows session (though not from other programs running in the same Windows session).<ref name="pcw199407_os2">{{ cite magazine | title=OS/2 for Windows | magazine=Personal Computer World | date=July 1994 | last1=Bidmead | first1=Chris | pages=251–252 }}</ref>

Whether Windows applications are running in full-screen or windowed mode, and in one Windows session or several, it is possible to use [[Dynamic Data Exchange|DDE]] between OS/2 and Windows applications, and [[Object Linking and Embedding|OLE]] between Windows applications only.<ref>{{cite web |title=OS/2 Warp Frequently Asked Questions List |author=Timothy F. Sipples |date=20 February 1995 |url=https://www.mit.edu/activities/os2/faq/os2faq0103.html}}</ref>

IBM's '''OS/2 for Windows''' product (codename Ferengi), also known as "OS/2, Special Edition", was interpreted as a deliberate strategy "of cashing in on the pervasive success of the Microsoft platform" but risked confusing consumers with the notion that the product was a mere accessory or utility running on Windows such as [[Norton Commander|Norton Desktop for Windows]] when, in fact, it was "a complete, modern, multi-tasking, pre-emptive operating system", itself hosting Windows instead of running on it. Available on CD-ROM or 18 floppy disks, the product documentation reportedly suggested Windows as a prerequisite for installing the product, also being confined to its original FAT partition, whereas the product apparently supported the later installation of Windows running from an HPFS partition, particularly beneficial for users of larger hard drives. Windows compatibility, relying on patching specific memory locations, was reportedly broken by the release of Windows 3.11, prompting accusations of arbitrary changes to Windows in order to perpetrate "a deliberate act of Microsoft sabotage" against IBM's product.<ref name="pcw199407_os2"/>