View source for CONFIG.SYS

{{Short description|System configuration file for DOS and OS/2}}
{{Use dmy dates|date=April 2019|cs1-dates=y}}
{{Use list-defined references |date=January 2022}}
{{Redirect-distinguish-for |SHELL|SHELL model||Shell (disambiguation)}}
'''CONFIG.SYS''' is the [[configuration file]] for the [[DOS]] and [[OS/2]] [[operating system]]s that specifies startup options {{endash}} options that cannot be changed after the system has [[booting|booted]]. The [[data]] it contains is read by the system and used to configure many aspects including [[memory management]], [[peripheral]]s and [[application software|applications]]. Each line can contain a [[name-value pair]] that is either a ''directive''<!--don't link to [[Directive (programming)]] since that's different--> that sets the value of a [[system setting]] or with name "DEVICE" extends system capability by loading a file such as a [[device driver]] or a [[terminate-and-stay-resident]] (TSR) program. CONFIG.SYS was introduced with DOS 2.0.<ref group="nb" name="NB_Durango_CONFIG.SYS"/>

As Windows technology diverged from DOS over time, use of CONFIG.SYS diminished. Both CONFIG.SYS and AUTOEXEC.BAT are in the [[Root directory|root folder]] of the [[Windows&nbsp;95]] and [[Windows&nbsp;98]] boot drives, but typically, they are empty. [[Windows&nbsp;Me]] does not use a CONFIG.SYS file at all.<ref name="Microsoft_2000_Windows-ME"/> Instead, it loads [[environment variable]]s from the [[Windows Registry]] key: <kbd>HKLM\System\CurrentControlSet\Control\SessionManager\Environment</kbd>.

==Use==
[[File:PC-MOS boot screen.png|thumb|[[PC-MOS]] detecting a missing {{code|CONFIG.SYS}} on startup]]

===User maintained===
The file is maintained by a [[computer user|user]] in order to control the behavior of the system. As an [[ASCII]] [[text file]], a user generally edits it via a [[text editor]].

===System consumed===
During boot, the [[DOS BIOS]]<ref>typically resides in [[IBMBIO.COM]] or [[IO.SYS]]</ref> loads the file from the [[root directory]] of the drive from which the system boots. After processing the file, the system loads and executes the [[command-line interpreter|command shell]] specified in the <kbd>SHELL</kbd> line, or [[COMMAND.COM]] if there is no such line. The command shell in turn is responsible for processing the [[AUTOEXEC.BAT]] file.

===Missing/corrupt===
Even though loading CONFIG.SYS is part of a normal bootup process, the system can boot if the file is missing or corrupt. A system probably requires troubleshooting if the file gets deleted or corrupted.

===Default shell===
If CONFIG.SYS does not contain a <kbd>SHELL</kbd> directive (or the file is corrupt or missing), DOS typically searches for COMMAND.COM in the root directory of the boot drive.<ref name="Paul_2004_YESCHAR"/> If this is not found, versions of DOS before 6.0 will not start up. MS-DOS 6.0/PC&nbsp;DOS 6.1 and Novell DOS 7<!-- not sure about PalmDOS right now --> and higher will instead display a prompt to enter the path and filename of a command processor. This recovery prompt is also displayed when the primary command processor is aborted due to faults or if it is exited deliberately.<ref name="Paul_1997_NWDOSTIP"/> (In the case of COMMAND.COM, the internal <code>EXIT</code> command is disabled only when the shell was started with <code>/P</code>.) This also provides limited means to replace the shell at [[runtime (program lifecycle phase)|runtime]] without having to reboot the system.
Since the MS-DOS 7.0 and higher COMMAND.COM executable is incompatible with DR-DOS,<ref name="Paul_2004_COMMAND"/> but typically resides in the root of drive C: in dual-boot scenarios with DR-DOS, DR-DOS 7.02 and higher no longer allow to bypass <kbd>SHELL</kbd> directives in ({{keypress|Ctrl}}+){{keypress|F5}}/{{keypress|F7}}/{{keypress|F8}} "skip"/"trace"/"step" modes.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/><ref name="Paul_2004_COMMAND"/> (Some later issues added ({{keypress|Ctrl}}+){{keypress|F6}} to reinvoke the former {{keypress|F5}} "skip" behaviour in order to allow recovery from problems with invalid <kbd>SHELL</kbd> arguments as well.<ref name="Paul_2004_YESCHAR"/>) Also, if no <kbd>SHELL</kbd> directive could be found when skipping CONFIG.SYS processing via ({{keypress|Ctrl}}+){{keypress|F5}} (and also with ({{keypress|Ctrl}}+){{keypress|F7}}/{{keypress|F8}}, when the default file extension has been changed with <code>SYS /DR:ext</code>),<ref name="Paul_2017_DR"/> the user is prompted to enter a valid shell file name ''before'' trying to load COMMAND.COM from the root.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_COMMAND"/> Pressing {{keypress|ENTER}} without specifying a file will assume the former default.<ref name="Paul_1997_OD-A3"/>

===File size limit===
Depending on the version, the size of the CONFIG.SYS file is limited to a few kilobytes under MS-DOS/PC&nbsp;DOS (up to 64&nbsp;KB in most recent versions), whereas the file's size is unlimited<!-- only limited by the file system --> under DR-DOS.<ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2004_YESCHAR"/> This is because the former operating systems (since DOS 3.0<ref name="Ernst_1987_DRIVER"/>) will compile the file into some tokenized in-memory representation<ref name="Ernst_1987_DRIVER"/> before they sort and regroup the directives to be processed in a specific order (with device drivers always being loaded before TSRs), whereas DR-DOS interprets the file and executes most directives line-by-line, thereby giving full control over the load order of drivers and TSRs via <kbd>DEVICE</kbd> and <kbd>INSTALL</kbd> (for example to solve load order conflicts or to load a program debugger before a device driver to be debugged)<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/> and allowing to adapt the user interaction and change the flow through the file based on conditions like processor types installed, any type of keys pressed, load or input errors occurring, or return codes given by loaded software.<ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_1997_OD-A3"/> This becomes particularly useful since <kbd>INSTALL</kbd> can also be used to run non-resident software under DR-DOS, so that temporary external programs can be integrated into the CONFIG.SYS control flow.<ref name="Paul_1997_NWDOSTIP"/><ref name="4DOS_8.00_HELP"/><ref name="Paul_1997_OD-A3"/>

===Data limits===
In MS-DOS/PC&nbsp;DOS 2.0 through 4.01, the length of the <kbd>SHELL</kbd> line was limited to 31 characters, whereas up to 128 characters are possible in later versions.<ref name="Paul_1997_NWDOSTIP"/><ref name="4DOS_8.00_HELP"/> DR-DOS even accepts up to 255 characters.<ref name="Paul_1997_NWDOSTIP"/><ref name="4DOS_8.00_HELP"/> CONFIG.SYS directives do not accept [[long filename]]s.

===Dual booting DOS and Windows 9x===
When installing [[Windows&nbsp;95]] over a preexisting DOS/Windows install, CONFIG.SYS and AUTOEXEC.BAT are renamed to CONFIG.DOS and AUTOEXEC.DOS. This is intended to ease dual booting between Windows&nbsp;9x and DOS. When booting into DOS, they are temporarily renamed CONFIG.SYS and AUTOEXEC.BAT. Backups of the Windows&nbsp;95 versions are made as CONFIG.W40 and AUTOEXEC.W40 files.

When Caldera DR-DOS 7.02/7.03 is installed on a system already containing Windows&nbsp;95, Windows' CONFIG.SYS and AUTOEXEC.BAT retain those names. DR-DOS' startup files are installed as DCONFIG.SYS (a name already used in earlier versions of DR DOS) and AUTODOS7.BAT.<ref name="Caldera_1998_USER"/>

===OS/2===
[[OS/2]] uses a CONFIG.SYS file for configuring options, drivers and environment before the graphical subsystem loads. There are many undocumented or poorly documented CONFIG.SYS directives used by OS/2.<ref name="Childs_1995_OS2"/> CONFIG.SYS continues to be used by the OS/2 derivatives [[eComStation]]<ref name="ecom_2001"/> and [[ArcaOS]].<ref name="ArcaOS_2020"/> In the OS/2 subsystem of [[Windows NT]], what appeared as CONFIG.SYS to OS/2 programs is actually stored in the registry.

== Example ==

An example CONFIG.SYS for MS-DOS 5:
<syntaxhighlight lang="ini" line="1">
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>

==Variations==
Some DOS variants load a file with an alternate name if its exists instead of loading from the default <kbd>CONFIG.SYS</kbd>:

; CCONFIG.SYS: While [[Concurrent DOS]] versions 3.2 to 4.1<!-- in 1985/1986 --> did not support CONFIG.SYS, later versions,<!-- since when exactly? --> [[Concurrent DOS 386]] and [[Concurrent DOS XM]]<!-- since 1987. What about Concurrent DOS 286? -->, as well as [[Multiuser DOS]], [[Datapac System Manager|System Manager]] and [[REAL/32]] load CCONFIG.SYS<!-- really CCONFIG.SYS, not CCONFIG.INI as under CCI Multiuser DOS? --> (initial "C" referring to "Concurrent") instead of CONFIG.SYS. Some versions of Multiuser&nbsp;DOS use a filename of CCONFIG.INI instead,<ref name="CCI_1997_PRINTDOC"/><ref name="CCI_1997_HELP"/> whereas <!-- probably other Multiuser DOS issues as well, and -->REAL/32<!-- 7.90--> is known to look for MCONFIG.SYS. These operating systems support many additional and different configuration settings (like <kbd>INIT_INSTALL</kbd>) not known under MS-DOS/PC&nbsp;DOS, but they are stored in the binary repository named CCONFIG.BIN rather than in CCONFIG.INI.<ref name="CCI_1997_PRINTDOC"/><ref name="CCI_1997_HELP"/> Both files are typically modified through a configuration utility named <kbd>CONFIG.EXE</kbd> only.<!-- This holds true at least for CCI Multiuser DOS 7.22 Gold. --><ref name="CCI_1997_PRINTDOC"/><ref name="CCI_1997_HELP"/>

; DCONFIG.SYS: [[DR DOS]]&nbsp;3.31, [[PalmDOS]]&nbsp;1.0, [[Novell&nbsp;DOS]]&nbsp;7, [[OpenDOS]]&nbsp;7.01, and DR-DOS&nbsp;7.02 and higher, a file named DCONFIG.SYS (initial "D" referring to "DR&nbsp;DOS"), if present, takes precedence over CONFIG.SYS.<ref name="Paul_1997_NWDOSTIP"/><ref name="Caldera_1998_USER"/><ref name="Paul_2004_CHAIN"/><ref name="Paul_2017_DR"/> Since DR&nbsp;DOS&nbsp;6.0, this was used in conjunction with disk compression software, where the original boot drive&nbsp;C: would become drive&nbsp;D: after loading the compression driver (and the "D" in the file name came in handy as well), but it is commonly used to help maintain multiple configuration files in multi-boot scenarios.

; ODCONFIG.SYS: OpenDOS&nbsp;7.01 and DR-OpenDOS&nbsp;7.02 look for a file named ODCONFIG.SYS,<ref name="Paul_1997_OD-A3"/><ref name="Paul_2001_NWDOSTIP"/><ref name="Paul_2004_CHAIN"/> whereas some issues of DR-DOS&nbsp;7.02 and higher instead also look for DRCONFIG.SYS.<ref name="Paul_2004_CHAIN"/>

: Under DR&nbsp;DOS&nbsp;6.0 and higher, the <code>SYS&nbsp;/DR:ext</code> command can be used to change the default file extensions.<ref name="Paul_1997_OD-A3"/><ref name="Novell_1993_LOADER"/><ref name="Paul_2017_DR"/> For example, with <code>SYS&nbsp;/L&nbsp;/DR:703</code> the written [[Volume Boot Record]] would look for a renamed and modified IBMBIO.703 system file (instead of the default [[IBMBIO.COM]]) and the IBMBIO.703 would look for IBMDOS.703 and [D]CONFIG.703 (instead of [[IBMDOS.COM]] and [D]CONFIG.SYS), so that multiple parallel sets of files can coexist in the same root directory and be selected via a boot-loader like LOADER, supplied with Multiuser DOS and DR-DOS 7.02/7.03.<ref name="Paul_1997_NWDOSTIP"/> The <kbd>SHELL</kbd> directive is enhanced to provide means to specify alternative AUTOEXEC.BAT files via <kbd>/P[:filename.ext]</kbd> and in this specific scenario, COMMAND.COM will accept file extensions other than "<code>.BAT</code>" as well (both features are also supported by [[4DOS]]).<ref name="4DOS_8.00_HELP"/> Under DR&nbsp;DOS&nbsp;6.0 and higher, the CONFIG.SYS directive <kbd>CHAIN=filespec</kbd> can be used to continue processing in the named file, which does not necessarily need to reside in the root directory of the boot drive.<ref name="Paul_1997_NWDOSTIP"/><ref name="Paul_2004_CHAIN"/> DR-DOS&nbsp;7.02 and higher optionally support an additional parameter as in <kbd>CHAIN=filespec,label</kbd> to jump to a specific <kbd>:label</kbd> in the given file.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2001_NWDOSTIP"/><ref name="Paul_2004_CHAIN"/>

: DR-DOS 7.03 and higher support a new <code>SYS&nbsp;/A</code> parameter in order to copy the corresponding CONFIG.SYS and AUTOEXEC.BAT files along with the system files.<ref name="Paul_2017_DR"/>

; FDCONFIG.SYS: Used by [[FreeDOS]].

; RXCONFIG.SYS: Used by [[RxDOS]]&nbsp;7.24 and higher.<ref name="RxDOS724"/>

; CONFIG.PTS: Used by [[PTS-DOS]].

Other variations include:
* CONFIG.SYS is used by {{ill|Disk Control Program|de}} (DCP), an MS-DOS derivative by the former East-German [[VEB Robotron]].<ref name="DCP_2016"/>
* Under [[FlexOS]]<!-- at least in FlexOS 286 1.13 as of 1986/1987 -->, CONFIG.SYS is a binary file defining the resource managers and device drivers loaded.

==Content==
The content of a CONFIG.SYS file and its many variants is described below. Each item describes a directive, load command or another syntactic element.

===Comment===
;{{visible anchor |REM}} {{nobold|(DOS 4.0 and DR DOS 3.31 and higher;<ref name="Paul_2004_YESCHAR"/> ignored under PTS-DOS)}} : Starts a comment as long as no text preceeds it on a line.

;{{visible anchor|;}} {{nobold|(DOS 6.0 and DR&nbsp;DOS 6.0 and higher)}} : Starts a comment and unlike {{mono|1=REM}} can follow a directive to form an in-line comment. See {{mono|1=COMMENT}}. In MS-DOS/PC&nbsp;DOS, the inline-comment is not ignored if put in double-quotes.

;{{visible anchor|*}} {{nobold|(PTS-DOS only)}} : Starts a comment like semi-colon (;).

===Load file===
;{{visible anchor |CALL}} {{nobold|(OS/2 4.0<!-- or 3.0? --> and higher only)}} : Similar to {{mono|1=INSTALL}} under DOS, loads programs in CONFIG.SYS. Similar to {{mono|1=RUN}} under OS/2, but runs in foreground and halts CONFIG.SYS processing until return.

;{{visible anchor |DEVICE}} {{nobold|(DOS 2.0 and DOS Plus 2.1 with FIDDLOAD and DR{{nbh}}DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Loads a device driver into memory.

;{{visible anchor |DEVICEHIGH}} {{nobold|(DOS 5.0 and DR{{nbh}}DOS 6.0 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Loads a device driver into upper memory. (Same as {{mono|1=HIDEVICE}} in DR{{nbh}}DOS 5.0.)

;{{visible anchor |HIDEVICE}} {{nobold|(DR&nbsp;DOS 5.0 and higher only)}} : See {{mono|1=DEVICEHIGH}}.

;{{visible anchor |HIINSTALL}} {{nobold|(DR&nbsp;DOS 5.0 and higher only)}} : See {{mono|1=INSTALLHIGH}}.

;{{visible anchor |HIINSTALLLAST}} {{nobold|(EDR-DOS 7.01.07 and DRMK only)}} : Installs a TSR program into memory, like {{mono|1=HIINSTALL}}, but installs after the DOS data segment relocation. Compare also: [[INSTCDEX]].

;{{visible anchor |INSTALL}} {{nobold|(DOS 4.0 and DR DOS 3.41<!-- or earlier? but not in 3.31 --> and higher<ref group="nb" name="pts"/>)}} : Installs a TSR program into memory.<ref name="Paul_1997_NWDOSTIP"/><ref name="4DOS_8.00_HELP"/>

;{{visible anchor |INSTALLHIGH}} {{nobold|(DOS 6.0 and DR&nbsp;DOS 6.0 and higher<ref group="nb" name="pts"/>)}} : Installs a TSR program into upper memory. (Same as {{mono|1=HIINSTALL}} in DR DOS 5.0.)

;{{visible anchor |INSTALLLAST}} {{nobold|(EDR-DOS 7.01.07 and DRMK only)}} : Installs a TSR program into memory, like {{mono|1=INSTALL}}, but installs after the DOS data segment relocation. Compare also: [[INSTCDEX]].

;{{visible anchor |RUN}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Similar to {{mono|1=CALL}}, loads programs in CONFIG.SYS. Similar to {{mono|1=INSTALL}} under DOS and {{mono|1=CALL}} under OS/2, but loads programs in background concurrently.

===Directive===

;{{visible anchor |ABORT}} {{nobold|(PTS-DOS only)}} : Specifies if programs can be aborted on errors.
;{{visible anchor |ACCDATE}} {{nobold|(MS-DOS 7.0 and higher only, ignored under DR-DOS 7.02 and higher)}}:<ref name="Paul_1997_OD-A3"/> Configures which drives should store file access date stamps in the [[FAT ACCDATE|reserved area]] of directory entries in [[File Allocation Table|FAT]] file systems.<ref name="Microsoft_1995_CONFIG"/><ref name="Microsoft_1998_CONFIG"/>
;{{visible anchor |AT}} {{nobold|(PTS-DOS only)}} : Conditional execution on AT-compatible machines only.
;{{visible anchor |AUTOCHECK}} {{nobold|(PTS-DOS only)}} : Boot manager.
;{{visible anchor |AUTOFAIL}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Configures verbosity of error messages.
;{{visible anchor |AUX}} {{nobold|(DR-DOS 7.02 and higher only)}} : Changes internal default serial device driver ({{mono|1=COM1:}} to {{mono|1=COM4:}}) for {{mono|1=AUX:}} device.<ref name="Paul_1997_OD-A3"/>
;{{visible anchor |AVAILDEV}} {{nobold|(DOS 2.0-2.1 and DR-DOS 7.02 and higher only<ref name="Paul_1997_OD-A3"/>)}} : Disables the availability of character devices outside phantom \DEV directory.
;{{visible anchor |BASEDEV}} {{nobold|(OS/2<ref group="nb" name="since2">at least since 2.0</ref> only)}} : Loads base device driver into memory.
;{{visible anchor |BEEP}} {{nobold|(DR-DOS 7.02 and higher only)}} : Emits a short beep, even if audible notifications are disabled via {{mono|1=SWITCHES=/Q}}.<ref name="Paul_1997_OD-A3"/>
;{{visible anchor |BOOTNEXT}} {{nobold|(DRMK only)}} : Specifies operating system to be booted.
;{{visible anchor |BREAK}} {{nobold|(DOS 2.0 and DR&nbsp;DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts">PTS-DOS also</ref>)}} : Sets or clears extended {{keypress|Ctrl|C}} checking.
;{{visible anchor |BUFFERS}} {{nobold|(DOS 2.0 and DR&nbsp;DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Specifies the number of disk buffers to allocate.
;{{visible anchor |BUFFERSHIGH}} {{nobold|(MS-DOS 7.0<ref name="Microsoft_1995_CONFIG"/> and DR-DOS 7.02 and higher<ref name="Paul_1997_OD-A3"/> and FreeDOS only)}} : Same as {{mono|1=BUFFERS}}, but explicitly loads buffers into HMA or UMB (like {{mono|1=HIBUFFERS}} under DR DOS 6.0 and higher).
;{{visible anchor |CACHESIZE}} {{nobold|(Embedded DOS 6-XL only)}} : Maximum number of 512-byte cache blocks dynamically allocated from system pool.
;{{visible anchor |CACHETTL}} {{nobold|(Embedded DOS 6-XL only)}} : Maximum time in ms before unused cache blocks are returned to system pool.
;{{visible anchor |CACHEFLUSH}} {{nobold|(Embedded DOS 6-XL only)}} : Maximum time in ms before a dirty cache block gets flushed to disk.
;{{visible anchor |CAPSLOCK}} {{nobold|(DR-DOS 7.02 and higher only)}} : Specifies whether the keyboard {{keypress|[[Caps Lock]]}} status is turned on or off.<ref name="Paul_1997_OD-A3"/>
;{{visible anchor |CDDNAME}} {{nobold|(PTS-DOS only)}} : Specifies the name of the CD-ROM hardware driver.
;{{visible anchor |CDDBUFFERS}} {{nobold|(PTS-DOS only)}} : Specifies the number of buffers for CD-ROM access.
;{{visible anchor |CLOCK}} {{nobold|(PTS-DOS only)}} : Specifies the type of clock used by the system.
;{{visible anchor |CODEPAGE}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies the OEM codepage(s).
;{{visible anchor |CMOSADDR}} {{nobold|(PTS-DOS only)}} : Specifies the address of the CMOS RAM.
;{{visible anchor |COLOR}} {{nobold|(PTS-DOS only)}} : Specifies colors for boot menus.
;{{visible anchor |COM1}} {{nobold|(DR-DOS 7.02 and higher only)}} : Defines count and logical order and configures I/O address and timeout for [[COM1]]: device.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2002_CTMOUSE"/>
;{{visible anchor |COM2}} {{nobold|(DR-DOS 7.02 and higher only)}} : Defines count and logical order and configures I/O address and timeout for [[COM2]]: device.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2002_CTMOUSE"/>
;{{visible anchor |COM3}} {{nobold|(DR-DOS 7.02 and higher only)}} : Defines count and logical order and configures I/O address and timeout for [[COM3]]: device.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2002_CTMOUSE"/>
;{{visible anchor |COM4}} {{nobold|(DR-DOS 7.02 and higher only)}} : Defines count and logical order and configures I/O address and timeout for [[COM4]]: device.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2002_CTMOUSE"/>
;{{visible anchor |COMAREA}} {{nobold|(PTS-DOS only)}} : Specifies buffer for DMA.
;{{visible anchor |COMMENT}} {{nobold|(DOS 4.0 and higher and RxDOS, ignored under DR-DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/> under Embedded DOS<ref group="nb" name="embed"/> and under PTS-DOS)}} : Redefines the lead-in character(s) for CONFIG.SYS inline-comments, or causes the following line to be ignored.
;{{visible anchor |COUNTRY}} {{nobold|(DOS 3.0 and DOS&nbsp;Plus 2.1 with [[FIDDLOAD]] and DR&nbsp;DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Enables and configures international support.
;{{visible anchor |CPOS}} {{nobold|(DR&nbsp;DOS 6.0 and higher only)}} : Sets display cursor to specified position for configuration menus.
;{{visible anchor |CPSW}} {{nobold|(MS-DOS 4.00-4.01 only, ignored under DR-DOS 7.02 and higher<ref name="Paul_1997_OD-A3"/>)}}: For codepage switching support.
;{{visible anchor |CPU}} {{nobold|(PTS-DOS only)}} : Specifies RAM refresh speed.
;{{visible anchor |CPU88}} {{nobold|(PTS-DOS only)}} : Conditional execution on 8088 CPUs only.
;{{visible anchor |CPU88+}} {{nobold|(PTS-DOS only)}} : Conditional execution on 8088 and higher CPUs only.
;{{visible anchor |CPU86}} {{nobold|(PTS-DOS only)}} : Conditional execution on 8086 CPUs only.
;{{visible anchor |CPU86+}} {{nobold|(PTS-DOS only)}} : Conditional execution on 8086/8088 and higher CPUs only.
;{{visible anchor |CPU286}} {{nobold|(PTS-DOS only)}} : Conditional execution on 286 CPUs only.
;{{visible anchor |CPU286+}} {{nobold|(PTS-DOS only)}} : Conditional execution on 286 and higher CPUs only.
;{{visible anchor |CPU386}} {{nobold|(DR-DOS 7.02 and higher<ref name="Paul_1997_OD-A3"/> and PTS-DOS only)}}: Conditional execution on 386 and higher CPUs only, i.e. {{code|1=CPU386 DEVICE=C:\DOS\EMM386.EXE}} or {{code|2=bat|CPU386 GOTO label386}}
;{{visible anchor |CPU386+}} {{nobold|(PTS-DOS only)}} : Conditional execution on 386 and higher CPUs only.
;{{visible anchor |CPU486}} {{nobold|(PTS-DOS only)}} : Conditional execution on 486 CPUs only.
;{{visible anchor |CPU486+}} {{nobold|(PTS-DOS only)}} : Conditional execution on 486 and higher CPUs only.

;{{visible anchor |DDSCS}} {{nobold|(EDR-DOS 7.01.07 only)}} : Configures the relocation of the drive descriptor tables.
;{{visible anchor |DEBLOCK}} {{nobold|(DR{{nbh}}DOS 6.0 (1993 update) and higher only)}} : Specifies the memory segment address up to which multi-sector disk data [[deblocking (data storage)|deblocking]] is allowed.
;{{visible anchor |DEBUG}} {{nobold|(DR{{nbh}}DOS 3.31 - 6.0 and 7.02 and higher only<ref name="Paul_1997_OD-A3"/>)}} : Enables internal debugger support.
;{{visible anchor |DEFAULT}} {{nobold|(PTS-DOS only)}} : Boot manager.
;{{visible anchor |DEVINFO}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Configures country and codepage information for KBD, SCR, LPT1, LPT2, LPT3 devices.
;{{visible anchor |DISKCACHE}} {{nobold|(OS/2<ref group="nb" name="since2"/> only, ignored under DR-DOS 7.02 and higher)}} : Configures cache memory sizes.
;{{visible anchor |DISKETTE}} {{nobold|(PTS-DOS only)}} : Specifies floppy disk compatibility mode.
;{{visible anchor |DISPLAY}} {{nobold|(PTS-DOS only)}} : Specifies display font.
;{{visible anchor |DOS}}<ref name="Schneider_1994"/> {{nobold|(DOS 5.0 and DR{{nbh}}DOS 6.0 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Specifies whether to load DOS into the [[high memory area]] and/or use upper memory. (Similar to {{mono|1=HIDOS=ON}} under DR{{nbh}}DOS 5.0.)
;{{visible anchor |DOSDATA}} {{nobold|(PC&nbsp;DOS 7.0 and higher, FreeDOS, EDR-DOS 7.01.07 and DRMK only)}} : Specifies whether to load DOS tables ({{mono|1=BUFFERS}}, {{mono|1=FCBS}}, {{mono|1=FILES}}, {{mono|1=LASTDRIVE}}, {{mono|1=STACKS}}) into upper memory.
;{{visible anchor |DOSDIR}} {{nobold|(PTS-DOS only)}} : Specifies alternative path to search for DOS files.
;{{visible anchor |DPBS}} {{nobold|(DRMK only)}}<!-- : . -->
;{{visible anchor |DPATH}} {{nobold|(OS/2 3.0 and higher only)}} : Specifies the search path for data files.
;{{visible anchor |DRIVATTR}} {{nobold|(PTS-DOS only)}} : Specifies physical parameters of disk drives.
;{{visible anchor |DRIVPARM}} {{nobold|(DOS 3.2<ref group="nb">apparently not functional in all PC DOS 3.x version</ref> and higher<ref group="nb" name="pts"/>)}} : Define parameters for unrecognized drives.
;{{visible anchor |DUMPPROCESS}} {{nobold|(OS/2 3.0 and higher only)}} : Enables and specifies drive for <code>PDUMP.nnn</code> error logs.
;{{visible anchor |ERREXE}} {{nobold|(PTS-DOS only)}} : Specifies if additional checks should be carried out when starting programs.
;{{visible anchor |ERROR}} {{nobold|(DR{{nbh}}DOS 6.0 and higher only)}} : Specifies an error / return code to be assumed in the following.
;{{visible anchor |EXECA20OFF}} {{nobold|(PTS-DOS only)}} : Specifies the state of the [[A20 gate]] when starting a program.
;{{visible anchor |FASTOPEN}} {{nobold|(DR{{nbh}}DOS 3.31 and higher and PTS-DOS only)}}: Specified the size of the hash table for fast file open operations. Works considerably differently from the external MS-DOS/PC&nbsp;DOS [[FASTOPEN (DOS command)|FASTOPEN]] driver.
;{{visible anchor |FCBS}} {{nobold|(DOS 3.0 and DR{{nbh}}DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Specifies the number of cached [[File Control Block|FCBs]] that can be opened at once. (Under DR-DOS, {{mono|1=FCBS}} and {{mono|1=FILES}} dynamically share the same internal buffer.)
; {{visible anchor |FCBSHIGH}} {{nobold|(MS-DOS 7.0<ref name="Microsoft_1995_CONFIG"/> and DR-DOS 7.02 and higher only<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/>)}} : Same as {{mono|1=FCBS}}, but explicitly loads FCBs into upper memory.
;{{visible anchor |FILENAME}} {{nobold|(PTS-DOS only)}} : Boot manager.
;{{visible anchor |FILES}} {{nobold|(DOS 2.0 and DR{{nbh}}DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Specifies the number of files that can be opened at once.
;{{visible anchor |FILESHIGH}} {{nobold|(MS-DOS 7.0<ref name="Microsoft_1995_CONFIG"/> and DR-DOS 7.02 and higher<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/> and FreeDOS only)}} : Same as {{mono|1=FILES}}, but explicitly loads file handles into upper memory.

;{{visible anchor |HIBUFFERS}} {{nobold|(DR&nbsp;DOS 6.0 and higher only)}} : See {{mono|1=BUFFERSHIGH}} or {{mono|1=DOS=HIGH,UMB}} or {{mono|1=DOSDATA}}.
;{{visible anchor |HIDOS}} {{nobold|(DR&nbsp;DOS 5.0 and higher only)}} : See {{mono|1=DOS=HIGH,UMB}}.
;{{visible anchor |HIFCBS}} {{nobold|(DR&nbsp;DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/> EDR-DOS 7.01.07 and DRMK only)}} : See {{mono|1=FCBSHIGH}} or {{mono|1=DOSDATA}}.
;{{visible anchor |HIFILES}} {{nobold|(DR&nbsp;DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/> EDR-DOS 7.01.07 and DRMK only)}} : See {{mono|1=FILESHIGH}} or {{mono|1=DOSDATA}}.
;{{visible anchor |HILASTDRIVE}} {{nobold|(DR-DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/> EDR-DOS 7.01.07 and DRMK only)}} : See {{mono|1=LASTDRIVEHIGH}} or {{mono|1=DOS=UMB}} or {{mono|1=DOSDATA}}.
;{{visible anchor |HISHELL}} {{nobold|(DR-DOS 7.02 and higher only)}} : See {{mono|1=SHELLHIGH}}.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="Paul_2004_YESCHAR"/>
;{{visible anchor |HISTACKS}} {{nobold|(DR-DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/> EDR-DOS 7.01.07 and DRMK only)}} : See {{mono|1=STACKSHIGH}} or {{mono|1=DOSDATA}}.
;{{visible anchor |HISTORY}} {{nobold|(DR&nbsp;DOS 3.41<!-- possibly 3.40+, definitely not 3.31 --> and higher only)}} : Enables and configures console and command line history buffer and extended pattern search functionality.
;{{visible anchor |HMAREA}} {{nobold|(PTS-DOS only)}} : Specifies the address of the HMA segment.
;{{visible anchor |IDLEHALT}} {{nobold|(FreeDOS only)}} : Configures HLT energy saving.
;{{visible anchor |IDTCHK}} {{nobold|(PTS-DOS only)}} : Specifies if the system should check for boot sector viruses.
;{{visible anchor |IFS}} {{nobold|(MS-DOS 4.00-4.01 only, ignored under DR-DOS 7.02 and higher; OS/2<ref group="nb" name="since2"/>)}} : Loads [[installable file system]]s.
;{{visible anchor |IOPL}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies programs (which would normally run at the CPU's [[IOPL]] [[Ring 3 (computer security)|ring 3]]) which should be allowed to run at [[ring 2 (computer security)|ring 2]] in order to directly access the hardware for I/O.
;{{visible anchor |INCLUDE}} {{nobold|(DOS 6.0 and higher, not DR-DOS, not FreeDOS)}} : Include directives from another menu block. (Can be emulated using {{mono|1=GOSUB}} and {{mono|1=RETURN}} under DR-DOS.)
;{{visible anchor |INSERT}} {{nobold|(DR-DOS 7.02 and higher only)}} : Specifies whether the keyboard {{keypress|Insert}} mode status is turned on or off.<ref name="Paul_1997_OD-A3"/>
;{{visible anchor |IRQPRIORITY}} {{nobold|(Embedded DOS 6-XL only)}} : Rotates PIC controller interrupt priorities so that specified number gets the highest priority

;{{visible anchor |KEYBOARD}} {{nobold|(PTS-DOS only)}} : Specifies the keyboard layout.
;{{visible anchor |KEYBUF}} {{nobold|(FreeDOS only)}} : Specifies the address of the relocated keyboard buffer.
;{{visible anchor |LASTDRIVE}} {{nobold|(DOS 3.0 and DOS&nbsp;Plus 2.1 with FIDDLOAD and DR&nbsp;DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Specifies the maximum of drives that can be accessed.
;{{visible anchor |LASTDRIVEHIGH}} {{nobold|(MS-DOS 7.0<ref name="Microsoft_1995_CONFIG"/> and DR-DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/> and FreeDOS only)}} : Same as LASTDRIVE, but explicitly loads the Current Directory Structure (CDS) into upper memory.
;{{visible anchor |LIBPATH}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies a list of search paths for DLLs.
;{{visible anchor |LOADFIX}} {{nobold|(PTS-DOS only)}} : Specifies how old programs should be handled.
;{{visible anchor |LOCKS}} {{nobold|(PTS-DOS only)}} : Specifies number of file locks.
;{{visible anchor |LOGO}} {{nobold|(MS-DOS 7.0 and higher and PTS-DOS only, ignored under DR-DOS 7.02 and higher)}} : Configures boot logo support under MS-DOS. Allows to display startup message in conjunction with PTS-DOS boot manager.
;{{visible anchor |LPT1}} {{nobold|(DR-DOS 7.02 and higher only)}} : Defines count and logical order and configures I/O address and timeout for [[LPT1]]: device.<ref name="Paul_1997_OD-A3"/>
;{{visible anchor |LPT2}} {{nobold|(DR-DOS 7.02 and higher only)}} : Defines count and logical order and configures I/O address and timeout for [[LPT2]]: device.<ref name="Paul_1997_OD-A3"/>
;{{visible anchor |LPT3}} {{nobold|(DR-DOS 7.02 and higher only)}} : Defines count and logical order and configures I/O address and timeout for [[LPT3]]: device.<ref name="Paul_1997_OD-A3"/>
;{{visible anchor |LPT4}} {{nobold|(some versions of DR-DOS 7.02 and higher only<ref name="Paul_1997_OD-A3"/>)}} : Enables, defines count and logical order and configures I/O address and timeout for [[LPT4]]: device.
;{{visible anchor |MAXWAIT}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies time before a waiting process gets a higher priority.
;{{visible anchor |MEMMAN}} {{nobold|(OS/2<!-- at least since 1.3 --> only)}} : Configures memory allocation strategy
;{{visible anchor |MEMORY}} {{nobold|(PTS-DOS only)}} : Specifies the default DOS memory allocation strategy.
;{{visible anchor |MENU}} {{nobold|(FreeDOS only)}} : Defines menu options.
;{{visible anchor |MENUCOLOR}} {{nobold|(DOS 6.0 and higher, not DR&nbsp;DOS, not FreeDOS)}} : Specifies menu colors. (Can be emulated using {{mono|1=ECHO}} under DR-DOS.)
;{{visible anchor |MENUDEFAULT}} {{nobold|(DOS 6.0 and higher and FreeDOS, not DR&nbsp;DOS)}} : Specifies the default menu block. (Can be emulated using {{mono|1=TIMEOUT}} and {{mono|1=SWITCH}} under DR-DOS.)
;{{visible anchor |MENUITEM}} {{nobold|(DOS 6.0 and higher, not DR&nbsp;DOS, not FreeDOS)}} : Specifies a menu block. (Can be emulated using {{mono|1=ECHO}} and {{mono|1=SWITCH}} under DR-DOS.)
;{{visible anchor |MULTITRACK}} {{nobold|(DOS 4.0 and DR-DOS 7.02 and higher;<ref name="Paul_1997_OD-A3"/> ignored under PTS-DOS)}} : Specifies whether multitrack disk operations are used or not.

;{{visible anchor |NOCHAR}} {{nobold|(DR-DOS 7.02 and higher only)}} : Specifies the default No ({{keypress|N}}) character in Yes/No/Resume questions.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="Paul_2004_YESCHAR"/>)

;{{visible anchor |NUMLOCK}} {{nobold|(DOS 6.0 and Novell DOS 7 and higher)}} : Specifies whether the keyboard [[Num Lock|{{keypress|Num Lock}}]] status is turned on or off.

;{{visible anchor |PAUSEONERROR}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies if user must acknowledge errors in CONFIG.SYS.

;{{anchor|PRINTMONBUFFER}} {{visible anchor |PRINTMONBUFSIZE}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Configures buffer size for LPT1, LPT2, LPT3.

;{{visible anchor |PC}} {{nobold|(PTS-DOS only)}} : Conditional execution on PC-compatible machines only.

;{{visible anchor |PRIORITY}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Configures priority scheduler.

;{{visible anchor |PRIORITY_DISK_IO}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Configures priority of programs using disk I/O.

;{{visible anchor |PRN}} {{nobold|(DR-DOS 7.02 and higher only)}}: Changes internal default printer device driver ({{mono|1=LPT1}} to {{mono|1=LPT3}}, or even {{mono|1=LPT4}}) for PRN device.<ref name="Paul_1997_OD-A3"/>

;{{visible anchor |PROTECTONLY}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies if DOS programs can be run or not.
;{{visible anchor |PROTSHELL}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Loads user interface.
;{{visible anchor |PS1}} {{nobold|(PTS-DOS only)}} : Conditional execution on [[IBM PS/1|PS/1]]-compatible machines only.
;{{visible anchor |PS2}} {{nobold|(PTS-DOS only)}} : Conditional execution on [[IBM PS/2|PS/2]]-compatible machines only.
;{{visible anchor |QUIET}} {{nobold|(PTS-DOS and DRMK only)}} : Mutes display output send to STDOUT.

;{{visible anchor |REIPL}} {{nobold|(OS/2 3.0 and higher only)}} : Specifies if system should reboot automatically on errors.
;{{visible anchor |RESERVEDRIVELETTER}} {{nobold|(OS/2 3 FixPack 24 and higher only)}} : Specifies a drive letter not to be used up for local block device drivers.
;{{visible anchor |RESUMECHAR}} {{nobold|(DR-DOS 7.02 and higher only)}}: Specifies the default Resume ({{keypress|R}}) character in Yes/No/Resume queries.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/>)
;{{visible anchor |RMSIZE}} {{nobold|(OS/2<ref group="nb" name="since2"/> only, ignored under DR-DOS 7.02 and higher)}} : Defines the real mode memory size.
;{{visible anchor |SAVENAME}} {{nobold|(PTS-DOS only)}} : Specifies, if the first character of deleted files should be stored in the [[FAT SAVENAME|reserved area]] of directory entries in the [[File Allocation Table|FAT]] file system.
;{{visible anchor |SCREEN}} {{nobold|(FreeDOS and PTS-DOS only)}} : Similar to {{mono|1=VIDEOMODE}} under PTS-DOS, specifies the video mode to be used under FreeDOS. Under PTS-DOS, {{mono|1=SCREEN}} does not specify the video mode but screen access methods.
;{{visible anchor |SCROLLOCK}} {{nobold|(DR-DOS 7.02 and higher only)}} : Specifies whether the keyboard [[Scroll Lock|{{keypress|Scroll Lock}}]] status is turned on or off.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/>)
;{{visible anchor |SET}} {{nobold|(DOS 6.0 and DR{{nbh}}DOS 6.0 and higher; OS/2<ref group="nb" name="since2"/>)}} : Sets environment variables.
;{{visible anchor |SHELL}} {{nobold|(DOS 2.0 and DR{{nbh}}DOS 3.31 and higher; OS/2<ref group="nb" name="since2"/><ref group="nb" name="pts"/>)}} : Loads the command interpreter shell.<ref name="Paul_2004_YESCHAR"/><ref name="Paul_2004_COMMAND"/>
;{{visible anchor |SHELLHIGH}} {{nobold|(DR-DOS 7.02 and higher and PTS-DOS and FreeDOS only)}} : Same as {{mono|1=SHELL}}, but supports an additional {{mono|1=SIZE}} parameter to define the size of the pre-allocation for COMMAND.COM to relocate its resident portion into the HMA (with <code>/MH</code>). Can be useful to avoid HMA fragmentation in conjunction with third-party shells which cannot load into the HMA. SHELLHIGH under PTS-DOS tries to load the shell into UMBs instead.)<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="4DOS_8.00_HELP"/><ref name="Paul_2004_YESCHAR"/>
;{{visible anchor |SHIFTSTATE}} {{nobold|(PTS-DOS only)}} : Specifies the state of the keyboard modifiers like Shift Lock, Num Lock, Scroll Lock or Insert mode.
;{{visible anchor |SHUTDOWN}} {{nobold|(PTS-DOS only)}} : Specifies if files should be closed on {{keypress|Ctrl|Alt|Del}}.
;{{visible anchor |SOFTREBOOT}} {{nobold|(PTS-DOS only)}} : Specifies if POST should be skipped on reboots.
;{{visible anchor |STACK}} {{nobold|(ignored under DR{{nbh}}DOS 3.31-5.0 and 7.02 and higher only)}} : Compatibility dummy - DR DOS 3.31 - 6.0 were mostly reentrant and had a different stacks layout.
;{{visible anchor |STACKS}} {{nobold|(DOS 3.2 and Novell DOS 7 and higher, ignored under DR DOS 6.0 and PTS-DOS)}} : Specifies the number of stacks for hardware interrupts.
;{{visible anchor |STACKSIZE}} {{nobold|(Embedded DOS 6-XL only)}} : Default stack size allocated for new threads.
;{{visible anchor |STACKSHIGH}} {{nobold|(MS-DOS 7.0<ref name="Microsoft_1995_CONFIG"/> and DR-DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/> and FreeDOS only)}} : Same as {{mono|1=STACKS}}, but explicitly loads buffers into upper memory.
;{{visible anchor |STORAGE}} {{nobold|(PTS-DOS only)}} : Boot manager.
;{{visible anchor |STRING}} {{nobold|(MS-DOS 3.0 only, ignored under DR-DOS 7.02 and higher)}} : Internal use.
;{{visible anchor |STUBA20}} {{nobold|(PTS-DOS only)}} : Specifies how XMS [[A20 gate]] control should work.
;{{visible anchor |SUBMENU}} {{nobold|(DOS 6.0 and higher, not DR{{nbh}}DOS, not FreeDOS)}} : Specifies a submenu block. (Can be emulated using {{mono|1=CLS}}, {{mono|1=ECHO}} and {{mono|1=SWITCH}} under DR-DOS.)
;{{visible anchor |SUPPRESSPOPUPS}} {{nobold|(OS/2 3.0 and higher only)}} : Specifies a drive where to log error information instead of displaying a textmode popup screen.
;{{visible anchor |SWAPPATH}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies swap file path.
;{{visible anchor |SWITCHAR}} {{nobold|(DOS 2.0-2.1, DOS Plus 2.1 with FIDDLOAD, DR-DOS 7.02 and higher,<ref name="Paul_1997_OD-A3"/> PTS-DOS, FreeDOS and RxDOS only)}}: Defines the default [[SwitChar]] used by the system (either '/' or '-').<ref name="4DOS_8.00_HELP"/>
;{{visible anchor |SWITCHES}} {{nobold|(DOS 4.0 and Novell DOS 7 and higher; ignored under PTS-DOS)}} : Specifies special options.<ref name="Paul_2004_YESCHAR"/><ref name="Paul_1997_OD-A3"/>
;{{visible anchor |SXFAKEHWFPU}} {{nobold|(OS/2 Warp 4 FixPak 1 (and higher) only)}} : Specifies if a fix for a FPU rounding bug should be activated or not.
;{{visible anchor |SYSBOOT}} {{nobold|(PTS-DOS only)}} : Specifies file name of alternative DOS operating systems to boot.
;{{visible anchor |SYSGEN}} {{nobold|(PTS-DOS only)}} : Configures the location of the various DOS parts in memory.
;{{visible anchor |SYSLOAD}} {{nobold|(PTS-DOS only)}} : Load system from alternative disk area.
;{{visible anchor |SYSTEMPOOL}} {{nobold|(Embedded DOS 6-XL only)}} : Size of system memory pool from which the system dynamically allocates for various purposes
;{{visible anchor |SYSTOUMB}} {{nobold|(PTS-DOS only)}} : Specifies if DOS data and code should be loaded into UMBs.
;{{visible anchor |THREADS}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies number of concurrent threads.
;{{visible anchor |TIMESLICE}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Configures minimum and maximum time slices for scheduler.
;{{visible anchor |TMPEXT}} {{nobold|(PTS-DOS only)}} : Specifies the file extension for temporary files.
;{{visible anchor |TRACE}} {{nobold|(DR-DOS 7.02 and higher and PTS-DOS only; OS/2<ref group="nb" name="since2"/>)}} : Globally or locally enables or disables CONFIG.SYS (and AUTOEXEC.BAT) single-stepping execution.<ref name="Paul_2004_YESCHAR"/><ref name="Paul_1997_OD-A3"/> The functionality under OS/2 differs significantly from that under DOS.
;{{visible anchor |TRACEBUF}} {{nobold|(OS/2<ref group="nb" name="since2"/> only)}} : Specifies size of {{mono|1=TRACE}} log buffer.
;{{visible anchor |TRAPDUMP}} {{nobold|(OS/2 3.0<!-- 4.0? --> and higher only)}} : Logs detailed error information.

;{{visible anchor |UMB}} {{nobold|(Embedded DOS<ref group="nb" name="embed"/> only)}} : Configures DOS management to use a specific segment as UMB memory.
;{{visible anchor |UMBSRV}} {{nobold|(PTS-DOS only)}} : Configures the UMB server used.
;{{visible anchor |USERAM}} {{nobold|(PTS-DOS only)}} : Specifies the address ranges used as UMB RAM.
;{{visible anchor |VERIFY}} {{nobold|(DR-DOS 7.02 and higher<ref name="Paul_1997_OD-A3"/> and Embedded DOS<ref group="nb" name="embed"/> only)}} : Enables or disables disk write verification.
;{{visible anchor |VERSION}} {{nobold|(FreeDOS, Embedded DOS,<ref group="nb" name="embed"/> and EDR-DOS 7.01.07 only)}} : Specifies the DOS version (and optionally the true DOS version) to be reported to programs.
;{{visible anchor |VGASCREEN}} {{nobold|(PTS-DOS only)}} : Configures VGA display status.
;{{visible anchor |VIDEOMODE}} {{nobold|(PTS-DOS only)}} : Similar to {{mono|1=SCREEN}} under FreeDOS, specifies current video mode.
;{{visible anchor |VIRTDMA}} {{nobold|(PTS-DOS only)}} : Specifies if virtual DMA can be used.
;{{visible anchor |VME}} {{nobold|(OS/2<!-- possibly only late versions --> only)}} : Specifies if the processor's [[Virtual Mode Extensions]] (VME) should be deactivated or not.
;{{visible anchor |VXD}} {{nobold|(PTS-DOS only)}} : Configures VxD driver for Windows.
;{{visible anchor |WINDOWS}} {{nobold|(PTS-DOS only)}} : Configures system support for Windows.
;{{visible anchor |XBDA}} {{nobold|(EDR-DOS 7.01.07 and DRMK only)}} : Configures the relocation of the extended BIOS data area (XBDA)
;{{visible anchor |XT}} {{nobold|(PTS-DOS only)}} : Conditional execution on XT-compatible machines only.
;{{visible anchor |YEAR2000}} {{nobold|(DR-DOS 7.02 and higher only)}} : Configures the built-in [[Year 2000 problem|Year 2000]] support.
;{{visible anchor |YESCHAR}} {{nobold|(PalmDOS 1.0, DR DOS 6.0 updates and Novell DOS 7 and higher only)}} : Specifies the default Yes ({{keypress|Y}}) character in Yes/No/Resume queries.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/>
;{{visible anchor |ZOMBIEDRV}} {{nobold|(PTS-DOS only)}} : Configures deletion tracking.

===User interaction===
;{{visible anchor|?}} {{nobold|(DR&nbsp;DOS 3.41<!-- or earlier? but not in 3.31 --> and higher, Embedded DOS<ref group="nb" name="embed">at least General Software Embedded DOS-ROM 4.1 and Embedded DOS 6-XL</ref> and FreeDOS only)}} : Displays a yes/no query and (since DR&nbsp;DOS 5.0) optional message to ask the user to confirm evaluation of subsequent directives.<ref name="Paul_2000_CONFIG"/> FreeDOS does not support optional messages, but optional conditions in conjunction with boot menus defined with {{mono|1=MENU}} and {{mono|1=MENUDEFAULT}}. DOS 6.0 and higher supports a similar feature by adding a {{mono|1=?}} after the name field, i.e. {{mono|1=DEVICE?}} instead of {{mono|1=?DEVICE}}. This variant is also supported by DR&nbsp;DOS.

;{{visible anchor|!}} {{nobold|(FreeDOS only)}} : Unconditionally evaluate the subsequent directive.

;{{visible anchor |CLS}} {{nobold|(DR&nbsp;DOS 6.0 and higher only)}} : Clears screen.

;{{visible anchor |ECHO}} {{nobold|(DR{{nbh}}DOS 5.0 and higher, and PTS-DOS and FreeDOS only)}} : Displays a message on screen.

;{{visible anchor |EECHO}} {{nobold|(FreeDOS only)}} : Displays a message including ANSI escape sequences.

;{{visible anchor |GETKEY}} {{nobold|(DR&nbsp;DOS 6.0 and higher only)}} : Waits for key or timeout and sets error level to pressed key's ASCII code; 1024 on timeout.

;{{visible anchor |PAUSE}} {{nobold|(PTS-DOS only)}} : Similar to {{mono|1=ECHO}} and {{mono|1=GETKEY}} under DR-DOS, displays text and waits for a key press.

;{{visible anchor |TIMEOUT}} {{nobold|(DR{{nbh}}DOS 6.0 and higher and PTS-DOS only)}} : Specifies the timeouts in CONFIG.SYS single-stepping and with {{mono|1=SWITCH}}, {{mono|1=GETKEY}} and {{mono|1=?}}, and the default answers for Yes/No queries and {{mono|1=SWITCH}} selections.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="Paul_2004_YESCHAR"/> PTS-DOS only supports the timeout value.

===Flow control===
;{{visible anchor|:}} {{nobold|(DR&nbsp;DOS 5.0 and higher only)}} : Defines a label to use as a jump target for {{mono|1=CHAIN}}, {{mono|1=DRSWITCH}}, {{mono|1=GOTO}}, {{mono|1=GOSUB}} and {{mono|1=SWITCH}}.

;{{visible anchor |CHAIN}} {{nobold|(DR&nbsp;DOS 5.0 and higher and Embedded DOS<ref group="nb" name="embed"/> only)}} : Continues processing in new file or (since DR-DOS 7.02) at a label.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_CHAIN"/>

;{{visible anchor |DRSWITCH}} {{nobold|(DR{{nbh}}DOS 7.02 and higher only)}} : See {{mono|1=SWITCH}}.<ref name="Paul_2000_CONFIG"/>

;{{visible anchor |EXIT}} {{nobold|(DR{{nbh}}DOS 6.0 and higher only)}} : Stops file processing before the end of the file has been reached (except for {{mono|1=SWITCHES}} and {{mono|1=SHELL}} directive processing under some conditions).

;{{visible anchor |FORCE}} {{nobold|(PTS-DOS only)}} : Include execution of specified CONFIG.SYS subsections. See {{mono|1=IGNORE}}.

;{{visible anchor |GOSUB}} {{nobold|(DR&nbsp;DOS 6.0 and higher only)}} : Continues processing at a label, with {{mono|1=RETURN}} returning to old location.<ref name="Paul_1997_OD-A3"/>

;{{visible anchor |GOTO}} {{nobold|(DR&nbsp;DOS 5.0 and higher only)}} : Continues processing at a label.

;{{visible anchor |IGNORE}} {{nobold|(PTS-DOS only)}} : Exclude execution of specified CONFIG.SYS subsections. See {{mono|1=FORCE}}.

;{{visible anchor |NEWFILE}} {{nobold|(Datalight ROM-DOS only)}} : Continues processing in new file (similar to DR-DOS [[#CHAIN|CHAIN]]) and optionally after loading a specific device driver and setting [[%NEWFILE%]] environment variable.<ref name="Datalight_2005_ROM-DOS"/>

;{{visible anchor |ONERROR}} {{nobold|(DR&nbsp;DOS 6.0 and higher only)}} : Conditional execution depending on last return code/error status only, i.e. {{code|2=bat|ONERROR > 0 GOTO failload}} or {{code|2=dosbatch|1=ONERROR > 10 ONERROR <> 17 ONERROR <= 30 ECHO Error 11-16 or 18-30 occurred}}.<ref name="Paul_1997_NWDOSTIP"/>

;{{visible anchor |RETURN}} {{nobold|(DR{{nbh}}DOS 6.0 and higher only)}} : Returns processing to the location of the last {{mono|1=GOSUB}} or {{mono|1=SWITCH}}. A return code can be specified but defaults to 0 if not specified.

;{{visible anchor |SWITCH}} {{nobold|(DR DOS 6.0 and higher only)}} : Conditionally continues processing at one of the specified labels depending on keys pressed, with {{mono|1=RETURN}} returning to old location.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="Paul_2004_YESCHAR"/>

== See also ==
* [[IBMBIO.COM]] / [[IO.SYS]]
* [[IBMDOS.COM]] / [[MSDOS.SYS]]
* [[CONFIG (environment variable)]]
* [[AUTOEXEC.BAT]]
* [[COMMAND.COM]]
* [[List of DOS commands]]

== Notes ==
{{Reflist|group="nb"|refs=
<ref group="nb" name="NB_Durango_CONFIG.SYS">The filename of the DOS configuration file <code>CONFIG.SYS</code> was derived from an identically named file used by the operating system [[Durango DX-85M|DX-85M]] for the [[Durango F-85]] family of computers introduced in 1978 - five years before the advent of [[MS-DOS 2.0]]/[[PC DOS 2.0]] in 1983. Both files are text files and use various directives to configure the system and load drivers, however, the syntax differs.</ref>
}}

== References ==
{{Reflist|refs=
<ref name="Paul_1997_NWDOSTIP">{{cite book |title=NWDOS-TIPs — Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |language=de |trans-title=Tips & tricks for Novell DOS 7, with a focus on undocumented details, bugs and workarounds |series=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=1997-07-30 |edition=3 |url=http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |access-date=2012-01-11 |url-status=dead |archive-url=https://web.archive.org/web/20161105172944/http://www.antonis.de/dos/dos-tuts/mpdostip/html/nwdostip.htm |archive-date=5 November 2016 }} (NB. NWDOSTIP.TXT is a comprehensive work on [[Novell DOS 7]] and [[OpenDOS 7.01]], including the description of many undocumented features and internals. It is part of the author's yet larger MPDOSTIP.ZIP collection maintained up to 2001 and distributed on many sites at the time. The provided link points to a HTML-converted older version of the NWDOSTIP.TXT file.)</ref>
<ref name="Caldera_1998_USER">{{cite book |publisher=[[Caldera, Inc.]] |date=1998 |orig-year=1993, 1997 |title=Caldera DR-DOS 7.02 User Guide |url=http://www.drdos.net/documentation/usergeng/uglontoc.htm |url-status=dead |archive-url=https://web.archive.org/web/20161104235434/http://www.drdos.net/documentation/usergeng/uglontoc.htm |archive-date=2016-11-04}}</ref>
<ref name="Paul_1997_OD-A3">{{cite web |author-first=Matthias R. |author-last=Paul |title=Caldera OpenDOS 7.01/7.02 Update Alpha 3 IBMBIO.COM README.TXT |url=http://www.uni-bonn.de/~uzs180/download/ibmbioa3.zip |date=1997-10-02 |access-date=2009-03-29 |url-status=dead |archive-url=https://web.archive.org/web/20031004074600/http://www-student.informatik.uni-bonn.de/~frinke/ibmbioa3.zip |archive-date=2003-10-04}} [https://web.archive.org/web/20181225154705/http://mirror.macintosharchive.org/max1zzz.co.uk/+Windows%20&%20DOS/DOS/System/Novell/Support/Bins/Op702src.zip<!-- Op702src.zip is an unofficial renamed distribution of the ibmbioa3.zip file -->]</ref>
<ref name="Paul_2001_NWDOSTIP">{{cite book |title=NWDOS-TIPs — Tips & Tricks rund um Novell DOS 7, mit Blick auf undokumentierte Details, Bugs und Workarounds |language=de |trans-title=Tips & tricks for Novell DOS 7, with a focus on undocumented details, bugs and workarounds |series=MPDOSTIP |author-first=Matthias R. |author-last=Paul |date=2001-04-09 |edition=3}}</ref>
<ref name="Novell_1993_LOADER">{{cite web |title=Booting Multiple Operating Systems with the DR Multiuser DOS LOADER Utility |archive-url=https://web.archive.org/web/20120322220335/http://developer.novell.com/support/bullets/apr93.htm |archive-date=2012-03-22 |url=http://developer.novell.com/support/bullets/apr93.htm#articles |series=Volume 5, Number 4 |author-first=Mad |author-last=Poarch<!-- Director, Developer Support/Service --> |publisher=[[Novell]] |date=April 1993 |access-date=2013-06-28 |url-status=dead}}</ref>
<ref name="4DOS_8.00_HELP">{{cite book |title=4DOS 8.00 online help |title-link=4DOS 8.00 |author-first1=Hardin |author-last1=Brothers |author-first2=Tom |author-last2=Rawson |author-link2=Tom Rawson |author-first3=Rex C. |author-last3=Conn |author-link3=Rex C. Conn |author-first4=Matthias R. |author-last4=Paul |author-first5=Charles E. |author-last5=Dye |author-first6=Luchezar I. |author-last6=Georgiev |date=2002-02-27}}</ref>
<ref name="Microsoft_2000_Windows-ME">{{cite web |title=Understanding the Settings in the Windows Millennium Edition CONFIG.SYS File |date=2007-01-29 |orig-year=2000 |version=Revision 1.2 |id=KB274646. Q274646 |publisher=[[Microsoft]] |access-date=2006-10-16 |url=http://support.microsoft.com/kb/q274646/ |url-status=dead |archive-url=https://archive.today/20120723153210/http://support.microsoft.com/kb/q274646 |archive-date=2012-07-23}}</ref>
<ref name="Microsoft_1995_CONFIG">{{cite web |title=Windows 95 CD-ROM CONFIG.TXT File - Microsoft Windows 95 README for MS-DOS Config.sys Commands |id=KB135481. Q135481 |version=Revision: 1.1 |publisher=[[Microsoft]] |date=2006-11-15 |orig-year=August 1995 |url=http://support.microsoft.com/kb/135481/EN-US |access-date=2011-12-22 |url-status=dead |archive-url=https://archive.today/20130128224809/http://support.microsoft.com/kb/135481/EN-US |archive-date=2013-01-28 |quote=[...] For each hard disk, specifies whether to record the date that files are last accessed. Last access dates are turned off for all drives when your computer is started in safe mode, and are not maintained for floppy disks by default. Syntax: <code>[[ACCDATE (CONFIG.SYS directive)|ACCDATE]]=drive1+{{!}}- [drive2+{{!}}-]...</code> [...]}}</ref>
<ref name="Microsoft_1998_CONFIG">{{cite web |title=The Windows 98 Config.txt File - Microsoft Windows 98 README for MS-DOS Config.sys Commands |publisher=[[Microsoft Corporation]] |id=ID 232557 |date=2017-01-07 |orig-year=April 1998 |edition=1 |url=http://support.microsoft.com/?kbid=232557 |access-date=2017-09-10 |url-status=dead |archive-url=https://web.archive.org/web/20180103011840/https://support.microsoft.com/en-us/help/232557/the-windows-98-config-txt-file |archive-date=2018-01-03}}</ref>
<ref name="Childs_1995_OS2">{{cite web |url=http://www.markcrocker.com/rexxtipsntricks/rxtt28.2.0795.html |title=CONFIG.SYS statements used by OS/2 |work=REXX Tips & Tricks, Version 2.80 |author-first=Peter |author-last=Childs |version=0.9b |date=1995 |access-date=2009-01-17 |url-status=dead |archive-url=https://web.archive.org/web/20120220031733/http://www.markcrocker.com/rexxtipsntricks/rxtt28.2.0795.html |archive-date=20 February 2012 }}</ref>
<ref name="Paul_2017_DR">{{cite web |title=The continuing saga of Windows 3.1 in enhanced mode on OmniBook 300 |author-first=Matthias R. |author-last=Paul |orig-year=2017-08-07 |date=2017-08-14 |work=MoHPC - the Museum of HP Calculators |url=http://hpmuseum.org/forum/thread-8774-post-77196.html#pid77196 |access-date=2018-05-01 |url-status=live |archive-url=https://web.archive.org/web/20180501185933/http://hpmuseum.org/forum/thread-8774-post-77196.html |archive-date=2018-05-01 |quote=[...] SYS [...] /A Additionally copy [D]CONFIG.SYS and AUTOEXEC.BAT file(s). [...] /B or /L Do not modify the Boot Sector in destination (with LOADER). [...] /DR[:ext] Use other file extension for system files (BIN) (with LOADER). [...]}}</ref>
<ref name="CCI_1997_HELP">{{cite book |title=CCI Multiuser DOS 7.22 GOLD Online Documentation |id=HELP.HLP |date=1997-02-10 |publisher=[[Concurrent Controls, Inc.]] (CCI)}}</ref>
<ref name="CCI_1997_PRINTDOC">{{cite book |title=CCI Multiuser DOS 7.22 GOLD Installation Guide |id=PRINTDOC.HLP |date=1997-02-10 |publisher=[[Concurrent Controls, Inc.]] (CCI)}}</ref>
<ref name="Datalight_2005_ROM-DOS">{{cite web |title=Datalight ROM-DOS User's Guide |date=April 2005 |orig-year=1999 |id=3010-0200-0716 |author1=Datalight, Inc. |author-link1=Datalight, Inc. |author2=GPvNO |publisher=[[Datalight, Inc.]] |url=https://www.datalight.com/assets/files/ROM-DOS_Users_Guide.pdf |access-date=2018-09-16 |url-status=live |archive-url=https://web.archive.org/web/20190421143059/https://www.datalight.com/assets/files/ROM-DOS_Users_Guide.pdf |archive-date=2019-04-21}}</ref>
<ref name="DCP_2016">{{cite web |title=Betriebssystem DCP |author-first1=Rüdiger |author-last1=Kurth |author-first2=Martin |author-last2=Groß |author-first3=Henry |author-last3=Hunger |date=2016-11-29 |orig-year=2007 |language=de |website=www.robotrontechnik.de |url=http://www.robotrontechnik.de/html/software/dcp.htm |access-date=2019-04-28 |url-status=live |archive-url=https://web.archive.org/web/20190403061152/http://www.robotrontechnik.de/html/software/dcp.htm |archive-date=2019-04-03}}</ref>
<ref name="Paul_2004_YESCHAR">{{cite web |title=Re: Random Lockups with DR-DOS 7.03 |date=2004-06-17 |author-first=Matthias R. |author-last=Paul |work=opendos@delorie.com; [[FidoNet]] conference: ALT_DOS |number=1 |url=https://fidonet.ozzmosis.com/echomail.php/alt_dos/7e55a758c10339d0.html |access-date=2019-04-28 |url-status=dead |archive-url=https://archive.today/20190428181923/https://fidonet.ozzmosis.com/echomail.php/alt_dos/7e55a758c10339d0.html |archive-date=28 April 2019 }} [https://archive.today/20190501023752/http://www.delorie.com/opendos/archives/browse.cgi?p=opendos/2004/06/17/07:47:11.1] [https://archive.today/20190428182007/http://www.fybertech.com/misc/qwkview/qwkview.pl?conf=3010]</ref>
<ref name="Paul_2004_CHAIN">{{cite web |title=Re: Random Lockups with DR-DOS 7.03 |date=2004-06-17 |number=2 |author-first=Matthias R. |author-last=Paul |work=opendos@delorie.com; [[FidoNet]] conference: ALT_DOS |url=https://fidonet.ozzmosis.com/echomail.php/alt_dos/f2b6d63fc10339d0.html |access-date=2019-04-28 |url-status=dead |archive-url=https://archive.today/20190428181843/https://fidonet.ozzmosis.com/echomail.php/alt_dos/f2b6d63fc10339d0.html |archive-date=28 April 2019 }} [https://archive.today/20190501023518/http://www.delorie.com/opendos/archives/browse.cgi?p=opendos/2004/06/17/07:47:11] [https://archive.today/20190428182007/http://www.fybertech.com/misc/qwkview/qwkview.pl?conf=3010]</ref>
<ref name="Paul_2004_COMMAND">{{cite web |title=Re: Random Lockups with DR-DOS 7.03 |date=2004-06-17 |number=3 |author-first=Matthias R. |author-last=Paul |work=opendos@delorie.com; [[FidoNet]] conference: ALT_DOS |url=https://fidonet.ozzmosis.com/echomail.php/alt_dos/e812a919c10339d0.html |access-date=2019-04-28 |url-status=dead |archive-url=https://archive.today/20190428181749/https://fidonet.ozzmosis.com/echomail.php/alt_dos/e812a919c10339d0.html |archive-date=2019-04-28 |quote=[...] all MS-DOS versions prior to Windows 95 [...] used a COM style COMMAND.COM file which has a special signature at the start of the file [...] queried by the MS-DOS BIOS before it loads the shell, but not by the DR-DOS BIOS [...] COMMAND.COM would [...] check that it is running on the "correct" DOS version, so if you would load their COMMAND.COM under DR-DOS, you would receive a "Bad version" error message and their COMMAND.COM would exit, so DR-DOS would [...] display an error message "Bad or missing command interpreter" (if DR-DOS was trying to load the SHELL= command processor after having finished CONFIG.SYS processing). In this case, you could enter the path to a valid DR-DOS COMMAND.COM (C:\DRDOS\COMMAND.COM) and everything was fine. Now, things have changed since MS-DOS 7.0 [...] COMMAND.COM has internally become an EXE style file, so there is no magic [...] signature [...] to check [...] thus no way for DR-DOS to rule out an incompatible COMMAND.COM. Further, their COMMAND.COM no longer does any version checks, but [...] does not work under DR-DOS [...] just crashes [...] the PC DOS COMMAND.COM works fine under DR-DOS [...]}} [https://archive.today/20190501023329/http://www.delorie.com/opendos/archives/browse.cgi?p=opendos/2004/06/17/06:23:16] [https://archive.today/20190428182007/http://www.fybertech.com/misc/qwkview/qwkview.pl?conf=3010]</ref>
<ref name="Paul_2000_CONFIG">{{cite web |title=Optimizing CONFIG.SYS... |date=2000-11-22 |author-first=Matthias R. |author-last=Paul |work=opendos@delorie.com |url=http://www.delorie.com/opendos/archives/browse.cgi?p=opendos/2000/11/22/11:09:09 |access-date=2019-05-06 |url-status=live |archive-url=https://archive.today/20190506023131/http://www.delorie.com/opendos/archives/browse.cgi?p=opendos/2000/11/22/11:09:09 |archive-date=2019-05-06}}</ref>
<ref name="RxDOS724">{{cite web |author=ecm |title=RxDOS 7.24 release |date=2018-10-08 |website=bttr-software.de |series=DOS ain't dead |url=http://www.bttr-software.de/forum/board_entry.php?id=15627 |access-date=2020-01-27 |url-status=live |archive-url=https://web.archive.org/web/20181215010804/http://www.bttr-software.de/forum/board_entry.php?id=15627 |archive-date=2018-12-15}}</ref>
<ref name="Paul_2002_CTMOUSE">{{cite web |title=Re: [fd-dev] ANNOUNCE: CuteMouse 2.0 alpha 1 |author-first=Matthias R. |author-last=Paul |work=freedos-dev |date=2002-04-06 |url=https://marc.info/?l=freedos-dev&m=101807226917577 |access-date=2020-02-07 |url-status=live |archive-url=https://web.archive.org/web/20200207130948/https://marc.info/?l=freedos-dev&m=101807226917577&w=2 |archive-date=2020-02-07 |quote=[...] [[DR-DOS 7.02]]+ has a [D]CONFIG.SYS directive to override the [[serial port]]s detected during System BIOS [[Power On Self Test|POST]], so tools like [[DEBUG (DOS command)|DEBUG]] [...] are no longer required to update or change the port settings in segment 40h. [...] insert a line to [D]CONFIG.SYS to make the port available to the [[System BIOS]], DOS, and most drivers and applications: [...] COM4=260,1 ; set [[I/O address]] for [[COM4]] to 260h, timeout 1 [...] Since old machines and DOS versions did not know about [[COM3]] and COM4 at all, good software will try to use the data stored in segment 0040h [...] Optionally hide the chosen mouse COM port from the system configuration to avoid any clobbering by old [[BASIC]] programs. [...]}}</ref>
<ref name="Ernst_1987_DRIVER">{{cite magazine |title=Damit die Scheibe spurt - 720 KB-Disketten mit MF-Drives im AT; Atari ST-Disketten unter DOS ab Version 3.2 in PCs, ATs oder Modell 30 |language=de |series=Programm |author-first1=Martin |author-last1=Ernst |author-first2=Detlef |author-last2=Grell |editor-first=Detlef |editor-last=Grell |date=November 1987 |magazine=[[c't - magazin für computertechnik]] |publisher=[[Verlag Heinz Heise GmbH & Co. KG]] |volume=1987 |issue=11 |issn=0724-8679 |pages=216-218, 220, 222, 224, 226, 228 [226<!-- relevant page -->]}}</ref>
<ref name="ecom_2001">{{cite web |url=http://www.ecomstation.com/docs/release1.0/ecs-ga-pdf-a5.pdf |date=2001 |access-date=2020-10-08 |website=ecomstation.com |title=eComStation 1.0 Manual}}</ref>
<ref name="ArcaOS_2020">{{cite web |url=https://www.arcanoae.com/wiki/arcaos/updating-from-a-prior-release/troubleshooting-the-arcaos-update-procedure/ |title=Troubleshooting the ArcaOS update procedure |access-date=2020-10-08 |website=arcanoae.com}}</ref>
<ref name="Schneider_1994">{{cite journal |title=Das Ende von DOS ist nur noch eine Frage der Zeit |language=de |trans-title=The end of DOS is only a question of time |author-first=Stefanie |author-last=Schneider |journal=[[Computerwoche]] |publisher=[[IDG Business Media GmbH]] |location=Munich, Germany |date=1994-06-17 |url=https://www.computerwoche.de/a/das-ende-von-dos-ist-nur-noch-eine-frage-der-zeit,1121952 |access-date=2022-01-02 |url-status=live |archive-url=https://web.archive.org/web/20220102151737/https://www.computerwoche.de/a/das-ende-von-dos-ist-nur-noch-eine-frage-der-zeit,1121952 |archive-date=2022-01-02 |quote=[...] So handelt es sich bei dem fuer Ende 1994, Anfang 1995 erwarteten [[MS-DOS 7.0]] offenkundig um eine der grafischen Benutzeroberflaeche entledigte Version von [[Windows 4.0]], die auch den Codenamen "[[Microsoft Chicago|Chicago]]" traegt. Dieses neue DOS soll der CW-Schwesterpublikation "PC-Welt" zufolge durch die neuen Parameter "standard" und "enhanced" in der Systemdatei Io.sys die leidigen Speicherbarrieren ueberwinden. [...]}} (NB. The undocumented settings <code>STANDARD</code> and <code>ENHANCED</code> are optional parameters of the CONFIG.SYS directive <kbd>[[DOS (CONFIG.SYS directive)|DOS]]</kbd>.)</ref>
}}

== External links ==
* {{cite web |title=AUTOEXEC.BAT and CONFIG.SYS information |date=2017-12-29 |publisher=Computer Hope |url=http://www.computerhope.com/ac.htm |access-date=2018-05-12 |url-status=live |archive-url=https://web.archive.org/web/20180512093519/https://www.computerhope.com/ac.htm |archive-date=2018-05-12}}
* {{cite web |title=Description of Windows 98 / MS-DOS 7.10 CONFIG.SYS directives |url=http://support.microsoft.com/?kbid=232557 |url-status=dead |archive-url=https://web.archive.org/web/20060212042929/http://support.microsoft.com/?kbid=232557 |archive-date=2006-02-12}}
* {{cite web |title=CONFIG.SYS Command Reference |date=1998 |publisher=[[Caldera (company)|Caldera]] |url=http://www.drdos.net/documentation/usergeng/09ugch9.htm#807 |access-date=2018-05-12 |url-status=dead |archive-url=https://web.archive.org/web/20180512093720/http://www.drdos.net/documentation/usergeng/09ugch9.htm |archive-date=2018-05-12}} (Description of DR-DOS 7 CONFIG.SYS directives (incomplete))
* {{cite web |title=Description of FreeDOS CONFIG.SYS directives |url=http://help.fdos.org/en/hhstndrd/cnfigsys/index.htm |access-date=2018-05-12 |url-status=live |archive-url=https://web.archive.org/web/20180512093840/http://help.fdos.org/en/hhstndrd/cnfigsys/index.htm |archive-date=2018-05-12}}
* {{cite web |title=PTS-DOS 2000 Pro User Manual including a description of PTS-DOS CONFIG.SYS directives (incomplete) |url=http://download.paragon-software.com/doc/manual_dos_eng.pdf |access-date=2018-05-12 |url-status=live |archive-url=https://web.archive.org/web/20180512094512/http://download.paragon-software.com/doc/manual_dos_eng.pdf |archive-date=2018-05-12}}
* {{cite web |title=Inoffizielle deutschsprachige PTS-DOS-FAQ (PTS/FAQD), unofficial PTS-DOS FAQ as of 2004-04-25, including more CONFIG.SYS directives |date=25 April 2004 |language=de |url=http://www.almnet.de/ptsdos/ptsfaqd.html |access-date=2018-05-12 |url-status=live |archive-url=https://web.archive.org/web/20180512093757/https://almnet.de/ptsdos/ptsfaqd.html |archive-date=2018-05-12}}

{{DOS system files}}

{{DEFAULTSORT:Config.Sys}}
[[Category:DOS configuration files]]
[[Category:OS/2 files]]
[[Category:Configuration files]]<!-- left in here, because also an OS/2 configuration files -->