Editing Configuration file (section)

===MS-DOS===
[[MS-DOS]] primarily relied on the <code>[[CONFIG.SYS]]</code> config file; a plain text file with simple key–value pairs (e.g. <code>DEVICEHIGH=C:\DOS\ANSI.SYS</code>). MS-DOS 6 introduced the INI-file format. Similar to an rc file, the [[batch file]] named <code>[[AUTOEXEC.BAT]]</code> ran commands on [[Booting|startup]]. Both these files were retained up to [[Windows 98SE]], which still ran on top of MS-DOS.

An example CONFIG.SYS:
<syntaxhighlight lang="ini">
DOS=HIGH,UMB
DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE RAM
DEVICEHIGH=C:\DOS\ANSI.SYS
FILES=30
SHELL=C:\DOS\COMMAND.COM C:\DOS /E:512 /P
</syntaxhighlight>

DOS applications used a wide variety of individual configuration files, most of them binary, proprietary and undocumented - and there were no common conventions or formats.{{citation needed|date=October 2016}}