Editing Windows 95 (section)

===Dependence on MS-DOS===
{{Main|MS-DOS 7}}
[[File:Microsoft Windows 95 Version 4.00.1111 command.com MS-DOS Prompt 492x259.png|thumb|250px|[[command.com]] running in a [[Windows console]] on Windows 95 (MS-DOS Prompt)]]
To end-users, MS-DOS appears as an underlying component of Windows 95. For example, it is possible to prevent the loading of the graphical user interface and boot the system into a real-mode MS-DOS environment. This was done by inserting [[command.com]] into the autoexec.bat file or changing the BootGUI variable in the MSDOS.SYS file to 0. This sparked debate amongst users and professionals regarding the extent to which Windows 95 is an operating system or merely a graphical shell running on top of MS-DOS.<ref name="oldnewthing2007" /><ref name="Schulman_1994_UnauthorizedWin95">{{cite book
 |title=Unauthorized Windows 95 - Developer's Resource Kit
 |last=Schulman
 |first=Andrew
 |date=October 1994
 |publisher=[[International Data Group|International Data Group Company]]
 |location=[[Foster City, California]]
 |isbn=1-56884-305-4<!-- 9781568841694 -->
 |oclc=300092018
}}</ref><ref name="Lea_1998_Cebit">{{cite web
 |title=Caldera shows Windows on DR-DOS, denying Microsoft claims
 |author-last=Lea
 |author-first=Graham
 |author-link=Graham Lea (journalist)
 |date=March 23, 1998
 |series=[[CeBIT]] news
 |location=Hanover, Germany
 |url=http://www.v3.co.uk/v3-uk/news/1996865/cebit-caldera-windows-dr-dos-denying-ms-claims
 |access-date=March 15, 2012
 |url-status=dead
 |archive-url=https://web.archive.org/web/20120315080721/http://www.v3.co.uk/v3-uk/news/1996865/cebit-caldera-windows-dr-dos-denying-ms-claims
 |archive-date=March 15, 2012
}}</ref>

When the graphical user interface is started, the virtual machine manager takes over the filesystem-related and disk-related functionality. MS-DOS itself is demoted to a compatibility layer for 16-bit device drivers.<ref name="oldnewthing2007"/> This contrasts with earlier versions of Windows which rely on MS-DOS to perform file and disk access (Windows for Workgroups 3.11 could also largely bypass MS-DOS when [[32-bit file access]] and [[32-bit disk access]] were enabled). Keeping MS-DOS in memory allows Windows 95 to use DOS device drivers when suitable Windows drivers are unavailable. Windows 95 is capable of using all 16-bit Windows 3.x drivers.

Unlike Windows 3.x, DOS programs running in Windows 95 do not need DOS drivers for the mouse, CD-ROM and sound card; Windows drivers are used instead. [[HIMEM.SYS]] is still required to boot Windows 95. [[EMM386]] and other memory managers, however, are only used by DOS programs. In addition, [[CONFIG.SYS]] and [[AUTOEXEC.BAT]] settings (aside from HIMEM.SYS) do not affect Windows programs. DOS games, which could not be executed on Windows 3.x, can run inside Windows 95 (games tended to lock up Windows 3.x or cause other problems). As with Windows 3.x, DOS programs that use [[Enhanced Graphics Adapter|EGA]] or [[Video Graphics Array|VGA]] graphics modes run in windowed mode ([[Color Graphics Adapter|CGA]] and [[text mode]] programs can continue to run).<ref name="oldnewthing2007" />

On startup, the MS-DOS component in Windows 95 responds to a pressed {{key press|F8}} key by temporarily pausing the default boot process and presenting the DOS boot options menu, allowing the user to continue starting Windows normally, start Windows in [[safe mode]] or exit to the DOS prompt.<ref name=" Schulman_1994_UnauthorizedWin95"/><!-- NB. The book discusses this for a beta version of Windows 95 with minor (non-significant) differences to how it works in the released versions. --> As in previous versions of [[MS-DOS]], there is no 32-bit support and DOS drivers must be loaded for mice and other hardware.

As a consequence of DOS compatibility, Windows 95 has to keep internal DOS data structures synchronized with those of Windows 95. When starting a program, even a native 32-bit Windows program, MS-DOS momentarily executes to create a data structure known as the [[Program Segment Prefix]]. It is even possible for MS-DOS to run out of [[conventional memory]] while doing so, preventing the program from launching.<ref name="Schulman_1994_UnauthorizedWin95"/> Windows 3.x allocated ''fixed'' segments in conventional memory first. Since the segments were allocated as fixed, Windows could not move them, which would prevent any more programs from launching.

Microsoft partially removed support for [[File Control Block]]s (an API hold-over of DOS 1.x and [[CP/M]]) in Windows 95 OSR2 ([[OEM]] Service Release 2). FCB functions can read [[FAT32]] volumes, but not write to them.

With merging Windows together with MS-DOS, Microsoft had effectively [[Vendor lock-in|locked-in]] users who may have been using a different non-Microsoft DOS, like [[PC DOS]] and [[DR DOS]], who could previously make use of Windows 3.x without requiring Microsoft's MS-DOS. [[Caldera (company)|Caldera]] demostrated that Windows 95 could in fact run on top of its DR DOS operating system, and argued that Microsoft was being anti-competitive, which would prove useful in a later [[Caldera v. Microsoft|court case]] between Caldera and Microsoft.<ref name="Romano_1998_Winbolt">{{cite journal |author-first=Mike |author-last=Romano |title=The mouse that roared. Forget the feds. It's up to an obscure Utah company to prove what we already know: that Microsoft is a monopoly. |journal=[[Seattle Weekly]] |date=1998-09-17 |orig-date=1998-09-16 |url=http://www.seattleweekly.com/1998-09-16/news/the-mouse-that-roared/ |access-date=2017-06-24 |url-status=dead |archive-url=https://web.archive.org/web/20170624231746/http://archive.seattleweekly.com/1998-09-16/news/the-mouse-that-roared/ |archive-date=2017-06-24 |quote=Furthermore, Caldera claims that Microsoft's flagship product, Windows 95, is nothing more than an "[[artificial tie]]" between its MS-DOS operating system and [[Microsoft Windows|Windows]] graphic interface with no business justification other than to keep competing underlying operating systems—like Caldera's DR-DOS—off the market. To prove its point, Caldera will soon release a piece of demonstration software called "[[WinBolt]]," which, it says, will allow users to install the Windows 95 interface atop DR-DOS. The demo will show, Caldera says, that there is no significant technological advancement, or justified business efficiency, to the combination of MS-DOS with Windows in Windows 95.}} [https://web.archive.org/web/20010211085804/http://www.seattleweekly.com/features/9837/features-romano.shtml]</ref><ref name="Schulman_2000_Dossier">{{cite web |title=The Caldera v. Microsoft Dossier |author-first=Andrew |author-last=Schulman |date=2000-02-07 |work=[[O'Reilly Network]] |publisher=[[O'Reilly and Associates, Inc.]] |url=http://www.oreillynet.com/pub/a/network/2000/02/07/schulman.html |url-status=dead |archive-url=https://web.archive.org/web/20000819023434/http://www.oreillynet.com/pub/a/network/2000/02/07/schulman.html |archive-date=2000-08-19}}</ref>