MS-DOS 7
MS-DOS 7 is a real mode operating system which has never been released separately by its creator Microsoft, but included in the Windows 9x family of operating systems. Windows 95 RTM reports to be MS-DOS 7.0, while Windows 95 OSR2, Windows 95 OSR2.5, Windows 98 and Windows 98SE report as 7.1.

Overview
A major difference between earlier versions of MS-DOS is the usage of the MSDOS.SYS file. In version 7 this is not a binary file, but a pure setting file. The older boot style, where Windows is not automatically started and the system boots into a DOS command shell, could keep on using that same style by setting BootGUI=0 in the MSDOS.SYS-file. Otherwise, Windows from Windows 95 onward will automatically start up on boot. However this was in reality only an automatic call for the command WIN.COM, the Windows starting program. Windows 95 and 98 are both dependent on MS-DOS to boot the 32 bits kernel and run legacy 16 bits MS-DOS device drivers, although MS-DOS 7 possibly is more "hidden" than earlier versions of MS-DOS. This is also true for Windows Millennium Edition, but "ME" prevents users from booting MS-DOS without booting the 32-bit Windows kernel. 
    
Also the paths for (a plausible but actually not necessary) Windows directory and Boot directory are to be set in this new version of the MSDOS.SYS file. Whilst IO.SYS (although binary different) remained as the initial executive startup file which BIOS booting routines fire up, if located correctly. Also the COMMAND.COM file implements the command prompt. The typical DOS setting files CONFIG.SYS and AUTOEXEC.BAT essentially retained their functions from earlier versions of MS-DOS (although memory allocation was no longer needed).

Although only included in Windows releases (the last official standalone release of MS-DOS ever was version 6.22), MS-DOS 7 can fairly easily be extracted from Windows 95/98, and be used alone on other computers, just as the earlier versions. Actually MS-DOS 7/7.1 works fine on many modern (as of 2016) motherboards (at least with PS2-keyboards), in sharp contrast to Windows 95/98. It has to be installed on a fairly small partition, located at "the top" of the hard drive and formatted as FAT. Another difference is that MS-DOS 7/7.1 requires a 80386 or higher processor, it fails to boot on 80286-class or lower x86 hardware. 

MS-DOS 7.1 added FAT32 support, while MS-DOS 7.0 and earlier versions of MS-DOS only supported FAT12 and FAT16. 

MS-DOS must be installed, prior to any Windows installation, through the SYS command (executing the SYS.COM file), preferably from a folder on a Ramdrive created by a bootable disc. Correct versions of IO.SYS (especially) must exist in the same folder as SYS.COM together with DRVSPACE.BIN, MSDOS.SYS, MSDOS.--- as well as COMMAND.COM, AUTOEXEC.BAT and CONFIG.SYS. All other files can be copied thereafter. (In Windows 95/98 they are found in either the root folder or in the C:\WINDOWS\COMMAND folder)

See also

 PC DOS 7
 List of DOS commands
 List of DOS system files
 Timeline of DOS operating systems

References

Notes
A.There was a "MS-DOS 7.1" made by China DOS Union, which is the same as the Windows 9x version, but bundled as a standalone OS with a multitude of utilities. Source: WinWorld.

Disk operating systems
Microsoft operating systems
Proprietary operating systems
1995 software