CONFIG.SYS

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Template:Short description Template:Use dmy dates Template:Use list-defined references Template:Redirect-distinguish-for CONFIG.SYS is the configuration file for the DOS and OS/2 operating systems that specifies startup options Template:Endash options that cannot be changed after the system has booted. The data it contains is read by the system and used to configure many aspects including memory management, peripherals and applications. Each line can contain a name-value pair that is either a directive 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 folder of the Windows 95 and Windows 98 boot drives, but typically, they are empty. Windows Me does not use a CONFIG.SYS file at all.<ref name="Microsoft_2000_Windows-ME"/> Instead, it loads environment variables from the Windows Registry key: HKLM\System\CurrentControlSet\Control\SessionManager\Environment.

Use

File:PC-MOS boot screen.png
PC-MOS detecting a missing Template:Code on startup

User maintained

The file is maintained by a 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 shell specified in the SHELL 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 SHELL 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 DOS 6.1 and Novell DOS 7 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 EXIT command is disabled only when the shell was started with /P.) This also provides limited means to replace the shell at 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 SHELL directives in (Template:Keypress+)Template:Keypress/Template:Keypress/Template:Keypress "skip"/"trace"/"step" modes.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/><ref name="Paul_2004_COMMAND"/> (Some later issues added (Template:Keypress+)Template:Keypress to reinvoke the former Template:Keypress "skip" behaviour in order to allow recovery from problems with invalid SHELL arguments as well.<ref name="Paul_2004_YESCHAR"/>) Also, if no SHELL directive could be found when skipping CONFIG.SYS processing via (Template:Keypress+)Template:Keypress (and also with (Template:Keypress+)Template:Keypress/Template:Keypress, when the default file extension has been changed with SYS /DR:ext),<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 Template:Keypress 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 DOS (up to 64 KB in most recent versions), whereas the file's size is unlimited 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 DEVICE and INSTALL (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 INSTALL 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 DOS 2.0 through 4.01, the length of the SHELL 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 filenames.

Dual booting DOS and Windows 9x

When installing Windows 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 9x and DOS. When booting into DOS, they are temporarily renamed CONFIG.SYS and AUTOEXEC.BAT. Backups of the Windows 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 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 CONFIG.SYS:

CCONFIG.SYS
While Concurrent DOS versions 3.2 to 4.1 did not support CONFIG.SYS, later versions, Concurrent DOS 386 and Concurrent DOS XM, as well as Multiuser DOS, System Manager and REAL/32 load CCONFIG.SYS (initial "C" referring to "Concurrent") instead of CONFIG.SYS. Some versions of Multiuser DOS use a filename of CCONFIG.INI instead,<ref name="CCI_1997_PRINTDOC"/><ref name="CCI_1997_HELP"/> whereas REAL/32 is known to look for MCONFIG.SYS. These operating systems support many additional and different configuration settings (like INIT_INSTALL) not known under MS-DOS/PC 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 CONFIG.EXE only.<ref name="CCI_1997_PRINTDOC"/><ref name="CCI_1997_HELP"/>
DCONFIG.SYS
DR DOS 3.31, PalmDOS 1.0, Novell DOS 7, OpenDOS 7.01, and DR-DOS 7.02 and higher, a file named DCONFIG.SYS (initial "D" referring to "DR 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 DOS 6.0, this was used in conjunction with disk compression software, where the original boot drive C: would become drive 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 7.01 and DR-OpenDOS 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 7.02 and higher instead also look for DRCONFIG.SYS.<ref name="Paul_2004_CHAIN"/>
Under DR DOS 6.0 and higher, the SYS /DR:ext 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 SYS /L /DR:703 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 SHELL directive is enhanced to provide means to specify alternative AUTOEXEC.BAT files via /P[:filename.ext] and in this specific scenario, COMMAND.COM will accept file extensions other than ".BAT" as well (both features are also supported by 4DOS).<ref name="4DOS_8.00_HELP"/> Under DR DOS 6.0 and higher, the CONFIG.SYS directive CHAIN=filespec 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 7.02 and higher optionally support an additional parameter as in CHAIN=filespec,label to jump to a specific :label 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 SYS /A 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 7.24 and higher.<ref name="RxDOS724"/>
CONFIG.PTS
Used by PTS-DOS.

Other variations include:

  • CONFIG.SYS is used by Template:Ill (DCP), an MS-DOS derivative by the former East-German VEB Robotron.<ref name="DCP_2016"/>
  • Under FlexOS, 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

Template:Visible anchor Template:Nobold
Starts a comment as long as no text preceeds it on a line.
Template:Visible anchor Template:Nobold
Starts a comment and unlike Template:Mono can follow a directive to form an in-line comment. See Template:Mono. In MS-DOS/PC DOS, the inline-comment is not ignored if put in double-quotes.
Template:Visible anchor Template:Nobold
Starts a comment like semi-colon (;).

Load file

Template:Visible anchor Template:Nobold
Similar to Template:Mono under DOS, loads programs in CONFIG.SYS. Similar to Template:Mono under OS/2, but runs in foreground and halts CONFIG.SYS processing until return.
Template:Visible anchor Template:Nobold
Loads a device driver into memory.
Template:Visible anchor Template:Nobold
Loads a device driver into upper memory. (Same as Template:Mono in DRTemplate:NbhDOS 5.0.)
Template:Visible anchor Template:Nobold
See Template:Mono.
Template:Visible anchor Template:Nobold
See Template:Mono.
Template:Visible anchor Template:Nobold
Installs a TSR program into memory, like Template:Mono, but installs after the DOS data segment relocation. Compare also: INSTCDEX.
Template:Visible anchor Template:Nobold
Installs a TSR program into memory.<ref name="Paul_1997_NWDOSTIP"/><ref name="4DOS_8.00_HELP"/>
Template:Visible anchor Template:Nobold
Installs a TSR program into upper memory. (Same as Template:Mono in DR DOS 5.0.)
Template:Visible anchor Template:Nobold
Installs a TSR program into memory, like Template:Mono, but installs after the DOS data segment relocation. Compare also: INSTCDEX.
Template:Visible anchor Template:Nobold
Similar to Template:Mono, loads programs in CONFIG.SYS. Similar to Template:Mono under DOS and Template:Mono under OS/2, but loads programs in background concurrently.

Directive

Template:Visible anchor Template:Nobold
Specifies if programs can be aborted on errors.
Template:Visible anchor Template:Nobold
<ref name="Paul_1997_OD-A3"/> Configures which drives should store file access date stamps in the reserved area of directory entries in FAT file systems.<ref name="Microsoft_1995_CONFIG"/><ref name="Microsoft_1998_CONFIG"/>
Template:Visible anchor Template:Nobold
Conditional execution on AT-compatible machines only.
Template:Visible anchor Template:Nobold
Boot manager.
Template:Visible anchor Template:Nobold
Configures verbosity of error messages.
Template:Visible anchor Template:Nobold
Changes internal default serial device driver (Template:Mono to Template:Mono) for Template:Mono device.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Disables the availability of character devices outside phantom \DEV directory.
Template:Visible anchor Template:Nobold
Loads base device driver into memory.
Template:Visible anchor Template:Nobold
Emits a short beep, even if audible notifications are disabled via Template:Mono.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Specifies operating system to be booted.
Template:Visible anchor Template:Nobold
Sets or clears extended Template:Keypress checking.
Template:Visible anchor Template:Nobold
Specifies the number of disk buffers to allocate.
Template:Visible anchor Template:Nobold
Same as Template:Mono, but explicitly loads buffers into HMA or UMB (like Template:Mono under DR DOS 6.0 and higher).
Template:Visible anchor Template:Nobold
Maximum number of 512-byte cache blocks dynamically allocated from system pool.
Template:Visible anchor Template:Nobold
Maximum time in ms before unused cache blocks are returned to system pool.
Template:Visible anchor Template:Nobold
Maximum time in ms before a dirty cache block gets flushed to disk.
Template:Visible anchor Template:Nobold
Specifies whether the keyboard Template:Keypress status is turned on or off.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Specifies the name of the CD-ROM hardware driver.
Template:Visible anchor Template:Nobold
Specifies the number of buffers for CD-ROM access.
Template:Visible anchor Template:Nobold
Specifies the type of clock used by the system.
Template:Visible anchor Template:Nobold
Specifies the OEM codepage(s).
Template:Visible anchor Template:Nobold
Specifies the address of the CMOS RAM.
Template:Visible anchor Template:Nobold
Specifies colors for boot menus.
Template:Visible anchor Template:Nobold
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"/>
Template:Visible anchor Template:Nobold
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"/>
Template:Visible anchor Template:Nobold
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"/>
Template:Visible anchor Template:Nobold
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"/>
Template:Visible anchor Template:Nobold
Specifies buffer for DMA.
Template:Visible anchor Template:Nobold
Redefines the lead-in character(s) for CONFIG.SYS inline-comments, or causes the following line to be ignored.
Template:Visible anchor Template:Nobold
Enables and configures international support.
Template:Visible anchor Template:Nobold
Sets display cursor to specified position for configuration menus.
Template:Visible anchor Template:Nobold
For codepage switching support.
Template:Visible anchor Template:Nobold
Specifies RAM refresh speed.
Template:Visible anchor Template:Nobold
Conditional execution on 8088 CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 8088 and higher CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 8086 CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 8086/8088 and higher CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 286 CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 286 and higher CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 386 and higher CPUs only, i.e. Template:Code or Template:Code
Template:Visible anchor Template:Nobold
Conditional execution on 386 and higher CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 486 CPUs only.
Template:Visible anchor Template:Nobold
Conditional execution on 486 and higher CPUs only.
Template:Visible anchor Template:Nobold
Configures the relocation of the drive descriptor tables.
Template:Visible anchor Template:Nobold
Specifies the memory segment address up to which multi-sector disk data deblocking is allowed.
Template:Visible anchor Template:Nobold
Enables internal debugger support.
Template:Visible anchor Template:Nobold
Boot manager.
Template:Visible anchor Template:Nobold
Configures country and codepage information for KBD, SCR, LPT1, LPT2, LPT3 devices.
Template:Visible anchor Template:Nobold
Configures cache memory sizes.
Template:Visible anchor Template:Nobold
Specifies floppy disk compatibility mode.
Template:Visible anchor Template:Nobold
Specifies display font.
Template:Visible anchor<ref name="Schneider_1994"/> Template:Nobold
Specifies whether to load DOS into the high memory area and/or use upper memory. (Similar to Template:Mono under DRTemplate:NbhDOS 5.0.)
Template:Visible anchor Template:Nobold
Specifies whether to load DOS tables (Template:Mono, Template:Mono, Template:Mono, Template:Mono, Template:Mono) into upper memory.
Template:Visible anchor Template:Nobold
Specifies alternative path to search for DOS files.
Template:Visible anchor Template:Nobold
Template:Visible anchor Template:Nobold
Specifies the search path for data files.
Template:Visible anchor Template:Nobold
Specifies physical parameters of disk drives.
Template:Visible anchor Template:Nobold
Define parameters for unrecognized drives.
Template:Visible anchor Template:Nobold
Enables and specifies drive for PDUMP.nnn error logs.
Template:Visible anchor Template:Nobold
Specifies if additional checks should be carried out when starting programs.
Template:Visible anchor Template:Nobold
Specifies an error / return code to be assumed in the following.
Template:Visible anchor Template:Nobold
Specifies the state of the A20 gate when starting a program.
Template:Visible anchor Template:Nobold
Specified the size of the hash table for fast file open operations. Works considerably differently from the external MS-DOS/PC DOS FASTOPEN driver.
Template:Visible anchor Template:Nobold
Specifies the number of cached FCBs that can be opened at once. (Under DR-DOS, Template:Mono and Template:Mono dynamically share the same internal buffer.)
Template:Visible anchor Template:Nobold
Same as Template:Mono, but explicitly loads FCBs into upper memory.
Template:Visible anchor Template:Nobold
Boot manager.
Template:Visible anchor Template:Nobold
Specifies the number of files that can be opened at once.
Template:Visible anchor Template:Nobold
Same as Template:Mono, but explicitly loads file handles into upper memory.
Template:Visible anchor Template:Nobold
See Template:Mono or Template:Mono or Template:Mono.
Template:Visible anchor Template:Nobold
See Template:Mono.
Template:Visible anchor Template:Nobold
See Template:Mono or Template:Mono.
Template:Visible anchor Template:Nobold
See Template:Mono or Template:Mono.
Template:Visible anchor Template:Nobold
See Template:Mono or Template:Mono or Template:Mono.
Template:Visible anchor Template:Nobold
See Template:Mono.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="Paul_2004_YESCHAR"/>
Template:Visible anchor Template:Nobold
See Template:Mono or Template:Mono.
Template:Visible anchor Template:Nobold
Enables and configures console and command line history buffer and extended pattern search functionality.
Template:Visible anchor Template:Nobold
Specifies the address of the HMA segment.
Template:Visible anchor Template:Nobold
Configures HLT energy saving.
Template:Visible anchor Template:Nobold
Specifies if the system should check for boot sector viruses.
Template:Visible anchor Template:Nobold
Loads installable file systems.
Template:Visible anchor Template:Nobold
Specifies programs (which would normally run at the CPU's IOPL ring 3) which should be allowed to run at ring 2 in order to directly access the hardware for I/O.
Template:Visible anchor Template:Nobold
Include directives from another menu block. (Can be emulated using Template:Mono and Template:Mono under DR-DOS.)
Template:Visible anchor Template:Nobold
Specifies whether the keyboard Template:Keypress mode status is turned on or off.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Rotates PIC controller interrupt priorities so that specified number gets the highest priority
Template:Visible anchor Template:Nobold
Specifies the keyboard layout.
Template:Visible anchor Template:Nobold
Specifies the address of the relocated keyboard buffer.
Template:Visible anchor Template:Nobold
Specifies the maximum of drives that can be accessed.
Template:Visible anchor Template:Nobold
Same as LASTDRIVE, but explicitly loads the Current Directory Structure (CDS) into upper memory.
Template:Visible anchor Template:Nobold
Specifies a list of search paths for DLLs.
Template:Visible anchor Template:Nobold
Specifies how old programs should be handled.
Template:Visible anchor Template:Nobold
Specifies number of file locks.
Template:Visible anchor Template:Nobold
Configures boot logo support under MS-DOS. Allows to display startup message in conjunction with PTS-DOS boot manager.
Template:Visible anchor Template:Nobold
Defines count and logical order and configures I/O address and timeout for LPT1: device.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Defines count and logical order and configures I/O address and timeout for LPT2: device.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Defines count and logical order and configures I/O address and timeout for LPT3: device.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Enables, defines count and logical order and configures I/O address and timeout for LPT4: device.
Template:Visible anchor Template:Nobold
Specifies time before a waiting process gets a higher priority.
Template:Visible anchor Template:Nobold
Configures memory allocation strategy
Template:Visible anchor Template:Nobold
Specifies the default DOS memory allocation strategy.
Template:Visible anchor Template:Nobold
Defines menu options.
Template:Visible anchor Template:Nobold
Specifies menu colors. (Can be emulated using Template:Mono under DR-DOS.)
Template:Visible anchor Template:Nobold
Specifies the default menu block. (Can be emulated using Template:Mono and Template:Mono under DR-DOS.)
Template:Visible anchor Template:Nobold
Specifies a menu block. (Can be emulated using Template:Mono and Template:Mono under DR-DOS.)
Template:Visible anchor Template:Nobold
Specifies whether multitrack disk operations are used or not.
Template:Visible anchor Template:Nobold
Specifies the default No (Template:Keypress) character in Yes/No/Resume questions.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="Paul_2004_YESCHAR"/>)
Template:Visible anchor Template:Nobold
Specifies whether the keyboard [[Num Lock|Template:Keypress]] status is turned on or off.
Template:Visible anchor Template:Nobold
Specifies if user must acknowledge errors in CONFIG.SYS.
Template:Anchor Template:Visible anchor Template:Nobold
Configures buffer size for LPT1, LPT2, LPT3.
Template:Visible anchor Template:Nobold
Conditional execution on PC-compatible machines only.
Template:Visible anchor Template:Nobold
Configures priority scheduler.
Template:Visible anchor Template:Nobold
Configures priority of programs using disk I/O.
Template:Visible anchor Template:Nobold
Changes internal default printer device driver (Template:Mono to Template:Mono, or even Template:Mono) for PRN device.<ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Specifies if DOS programs can be run or not.
Template:Visible anchor Template:Nobold
Loads user interface.
Template:Visible anchor Template:Nobold
Conditional execution on PS/1-compatible machines only.
Template:Visible anchor Template:Nobold
Conditional execution on PS/2-compatible machines only.
Template:Visible anchor Template:Nobold
Mutes display output send to STDOUT.
Template:Visible anchor Template:Nobold
Specifies if system should reboot automatically on errors.
Template:Visible anchor Template:Nobold
Specifies a drive letter not to be used up for local block device drivers.
Template:Visible anchor Template:Nobold
Specifies the default Resume (Template:Keypress) character in Yes/No/Resume queries.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/>)
Template:Visible anchor Template:Nobold
Defines the real mode memory size.
Template:Visible anchor Template:Nobold
Specifies, if the first character of deleted files should be stored in the reserved area of directory entries in the FAT file system.
Template:Visible anchor Template:Nobold
Similar to Template:Mono under PTS-DOS, specifies the video mode to be used under FreeDOS. Under PTS-DOS, Template:Mono does not specify the video mode but screen access methods.
Template:Visible anchor Template:Nobold
Specifies whether the keyboard [[Scroll Lock|Template:Keypress]] status is turned on or off.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/>)
Template:Visible anchor Template:Nobold
Sets environment variables.
Template:Visible anchor Template:Nobold
Loads the command interpreter shell.<ref name="Paul_2004_YESCHAR"/><ref name="Paul_2004_COMMAND"/>
Template:Visible anchor Template:Nobold
Same as Template:Mono, but supports an additional Template:Mono parameter to define the size of the pre-allocation for COMMAND.COM to relocate its resident portion into the HMA (with /MH). 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"/>
Template:Visible anchor Template:Nobold
Specifies the state of the keyboard modifiers like Shift Lock, Num Lock, Scroll Lock or Insert mode.
Template:Visible anchor Template:Nobold
Specifies if files should be closed on Template:Keypress.
Template:Visible anchor Template:Nobold
Specifies if POST should be skipped on reboots.
Template:Visible anchor Template:Nobold
Compatibility dummy - DR DOS 3.31 - 6.0 were mostly reentrant and had a different stacks layout.
Template:Visible anchor Template:Nobold
Specifies the number of stacks for hardware interrupts.
Template:Visible anchor Template:Nobold
Default stack size allocated for new threads.
Template:Visible anchor Template:Nobold
Same as Template:Mono, but explicitly loads buffers into upper memory.
Template:Visible anchor Template:Nobold
Boot manager.
Template:Visible anchor Template:Nobold
Internal use.
Template:Visible anchor Template:Nobold
Specifies how XMS A20 gate control should work.
Template:Visible anchor Template:Nobold
Specifies a submenu block. (Can be emulated using Template:Mono, Template:Mono and Template:Mono under DR-DOS.)
Template:Visible anchor Template:Nobold
Specifies a drive where to log error information instead of displaying a textmode popup screen.
Template:Visible anchor Template:Nobold
Specifies swap file path.
Template:Visible anchor Template:Nobold
Defines the default SwitChar used by the system (either '/' or '-').<ref name="4DOS_8.00_HELP"/>
Template:Visible anchor Template:Nobold
Specifies special options.<ref name="Paul_2004_YESCHAR"/><ref name="Paul_1997_OD-A3"/>
Template:Visible anchor Template:Nobold
Specifies if a fix for a FPU rounding bug should be activated or not.
Template:Visible anchor Template:Nobold
Specifies file name of alternative DOS operating systems to boot.
Template:Visible anchor Template:Nobold
Configures the location of the various DOS parts in memory.
Template:Visible anchor Template:Nobold
Load system from alternative disk area.
Template:Visible anchor Template:Nobold
Size of system memory pool from which the system dynamically allocates for various purposes
Template:Visible anchor Template:Nobold
Specifies if DOS data and code should be loaded into UMBs.
Template:Visible anchor Template:Nobold
Specifies number of concurrent threads.
Template:Visible anchor Template:Nobold
Configures minimum and maximum time slices for scheduler.
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Specifies the file extension for temporary files.
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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.
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Specifies size of Template:Mono log buffer.
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Logs detailed error information.
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Configures DOS management to use a specific segment as UMB memory.
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Configures the UMB server used.
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Specifies the address ranges used as UMB RAM.
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Enables or disables disk write verification.
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Specifies the DOS version (and optionally the true DOS version) to be reported to programs.
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Configures VGA display status.
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Similar to Template:Mono under FreeDOS, specifies current video mode.
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Specifies if virtual DMA can be used.
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Specifies if the processor's Virtual Mode Extensions (VME) should be deactivated or not.
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Configures VxD driver for Windows.
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Configures system support for Windows.
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Configures the relocation of the extended BIOS data area (XBDA)
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Conditional execution on XT-compatible machines only.
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Configures the built-in Year 2000 support.
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Specifies the default Yes (Template:Keypress) character in Yes/No/Resume queries.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2004_YESCHAR"/>
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Configures deletion tracking.

User interaction

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Displays a yes/no query and (since DR 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 Template:Mono and Template:Mono. DOS 6.0 and higher supports a similar feature by adding a Template:Mono after the name field, i.e. Template:Mono instead of Template:Mono. This variant is also supported by DR DOS.
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Unconditionally evaluate the subsequent directive.
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Clears screen.
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Displays a message on screen.
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Displays a message including ANSI escape sequences.
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Waits for key or timeout and sets error level to pressed key's ASCII code; 1024 on timeout.
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Similar to Template:Mono and Template:Mono under DR-DOS, displays text and waits for a key press.
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Specifies the timeouts in CONFIG.SYS single-stepping and with Template:Mono, Template:Mono and Template:Mono, and the default answers for Yes/No queries and Template:Mono 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

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Defines a label to use as a jump target for Template:Mono, Template:Mono, Template:Mono, Template:Mono and Template:Mono.
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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"/>
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See Template:Mono.<ref name="Paul_2000_CONFIG"/>
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Stops file processing before the end of the file has been reached (except for Template:Mono and Template:Mono directive processing under some conditions).
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Include execution of specified CONFIG.SYS subsections. See Template:Mono.
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Continues processing at a label, with Template:Mono returning to old location.<ref name="Paul_1997_OD-A3"/>
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Continues processing at a label.
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Exclude execution of specified CONFIG.SYS subsections. See Template:Mono.
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Continues processing in new file (similar to DR-DOS CHAIN) and optionally after loading a specific device driver and setting %NEWFILE% environment variable.<ref name="Datalight_2005_ROM-DOS"/>
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Conditional execution depending on last return code/error status only, i.e. Template:Code or Template:Code.<ref name="Paul_1997_NWDOSTIP"/>
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Returns processing to the location of the last Template:Mono or Template:Mono. A return code can be specified but defaults to 0 if not specified.
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Conditionally continues processing at one of the specified labels depending on keys pressed, with Template:Mono returning to old location.<ref name="Paul_1997_OD-A3"/><ref name="Paul_2000_CONFIG"/><ref name="Paul_2004_YESCHAR"/>

See also

Notes

Template:Reflist

References

Template:Reflist

Template:DOS system files

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