DOS CONFIG.SYS commands

REM

BREAK

DOS 2.0 and above

Sets or clears extended CTRL+C checking.

BREAK=ON|OFF
The default setting is BREAK OFF.

BUFFERS

DOS 2.0 and above

Allocates disk buffers.

BUFFERS=n[,m][/X]

  n           Specifies the number of disk buffers from 1 to 99.
  m           Specifies the number of readahead sector buffers from 0 to 8.
  /X          Specifies that buffers are to be loaded in expanded memory (EMS).
m is only available in DOS 4 and above.
/X is only available in DOS 4.
For DOS 2.0 to 3.1 the default setting is BUFFERS=2.
For DOS 3.2 the default setting is BUFFERS=2 if only 360K floppy drives are detected and BUFFERS=3 otherwise.
For DOS 3.3 and above the default setting depends on the amount of conventional memory:
 less than 128K: same as DOS 3.2
 128K to 255K: BUFFERS=5
 256K to 511K: BUFFERS=10
 512K to 640K: BUFFERS=15

COMMENT

DOS 4.0 and above

Specifies a comment sequence.

COMMENT [delimiter]

  delimiter   Specifies a one or two byte comment sequence. Any CONFIG.SYS
              lines starting with the sequence will be treated as comments.
In DOS 6 and above CONFIG.SYS lines starting with ; are treated as comments.

COUNTRY

MS-DOS 2.01 and above; PC DOS 3.0 and above

Enables international support.

COUNTRY=xxx[,[yyy][,[drive:][path]filename]]

   xxx        Specifies the country code.
   yyy        Specifies the code page for the country.
   filename   Specifies the location and name of the file containing
              country information.
yyy and filename are only available in DOS 3.3 and above.
The default country information file is COUNTRY.SYS in the root directory of the boot drive.

DEVICE

DOS 2.0 and above

Loads a device driver.

DEVICE=[drive:][path]filename [parameters]

  filename    Specifies the filename of the device driver to load.
  parameters  Specifies the parameters to pass to the device driver.

DEVICEHIGH

DOS 5.0 and above

Loads a device driver into upper memory.

DEVICEHIGH=[drive:][path]filename [parameters]
DEVICEHIGH=[/L:region1[,minsize1][;region2[,minsize2]...] [/S]]
           [drive:][path]filename [parameters]

  /L:region1[,minsize1][;region2[,minsize2]]...
              Specifies the region(s) of memory into which to load
              the program.  Region1 specifies the number of the first
              memory region; minsize1 specifies the minimum size, if
              any, for region1.  Region2 and minsize2 specify the
              number and minimum size of the second region, if any.
              You can specify as many regions as you want.
  /S          Shrinks a UMB to its minimum size while the program
              is loading.
  filename    Specifies the filename of the device driver to load.
  parameters  Specifies the parameters to pass to the device driver.
/L and /S are only available in DOS 6 and above.

DOS

DOS 5.0 and above

Specifies where to load DOS.

DOS=HIGH|LOW[,UMB|,NOUMB]

  HIGH        Load DOS into the high memory area (HMA) if available.
  LOW         Load DOS into conventional memory.
  UMB         Allocate upper memory blocks (UMBs) so programs can load there.
  NOUMB       Do not allocate upper memory blocks.
If DOS=HIGH is used then DOS will load disk buffers into the high memory area if sufficient memory is available.
Use of the high memory area or upper memory blocks requires an XMS extended memory manager such as HIMEM.SYS.

DOSDATA

PC DOS 7.0

Loads DOS tables into upper memory.

DOSDATA=UMB|NOUMB

  UMB         Load DOS data tables (FILES, FCBS, BUFFERS, LASTDRIVE, STACKS)
              into upper memory.
  NOUMB       Do not load DOS data tables into upper memory.

DRIVPARM

DOS 3.2 and above

Specifies internal drive parameters.

DRIVPARM=/D:number [/C] [/F:factor] [/H:heads] [/I] [/N]
         [/S:sectors] [/T:tracks]

  /D:number   Specifies the physical drive number.
  /C          Specifies that the drive has changeline support.
  /F:factor   Specifies the drive form factor:
                0  160K/180K or 320K/360K
                1  1.2M
                2  720K (3.5-inch disk)
                5  Hard disk
                6  Tape
                7  1.44M (3.5-inch disk)
                8  Read/write optical disk
                9  2.88M (3.5-inch disk)
  /H:heads    Specifies the maximum number of heads.
  /I          Specifies an electronically compatible 3.5-inch
              floppy disk drive.
  /N          Specifies a nonremovable block device.
  /S:sectors  Specifies the number of sectors per track.
  /T:tracks   Specifies the number of tracks.
/I is only available in DOS 5 and above.

FCBS

DOS 3.0 and above

Allocates FCB system file tables.

FCBS=n[,m]

  n           Specifies the number of FCB system file tables from 1 to 255.
  m           Specifies the FCB keep count from 0 to 255.
The default setting is FCBS=4,0.

FILES

DOS 2.0 and above

Allocates system file tables.

FILES=n

  n           Specifies the number of system file tables from 8 to 255.
The default setting is FILES=8.

INCLUDE

DOS 6.0 and above

Includes a configuration block.

INCLUDE=blockname

   blockname  Specifies the name of the configuration block to include.

INSTALL

DOS 4.0 and above

Loads a resident program.

INSTALL=[drive:][path]filename [parameters]

  filename    Specifies the filename of the program to load.
  parameters  Specifies the parameters to pass to the program.

INSTALLHIGH

DOS 6.0 and above

Loads a resident program into upper memory.

INSTALLHIGH=[drive:][path]filename [parameters]

  filename    Specifies the filename of the program to load.
  parameters  Specifies the parameters to pass to the program.

LASTDRIVE

DOS 3.0 and above

Allocates drive tables.

LASTDRIVE=x

  x           Specifies the last drive letter allocated from A to Z.
The default setting is one more than the last drive detected.
The drive tables are known as current directory structures.

MENUCOLOR

DOS 6.0 and above

Specifies the startup menu color.

MENUCOLOR=x[,y]

  x           Specifies the foreground color of the menu text from 0 to 15.
  y           Specifies the background color of the menu text from 0 to 15.

MENUDEFAULT

DOS 6.0 and above

Specifies the default startup menu item.

MENUDEFAULT=blockname[,timeout]

  blockname   Specifies the default menu item by its associated
              configuration block.
  timeout     Specifies the length in seconds that DOS must wait before
              starting your computer with the default configuration.
              If you do not specify a timeout value, DOS does not
              continue until you press Enter.

MENUITEM

DOS 6.0 and above

Specifies a startup menu item.

MENUITEM=blockname[,menu_text]

  blockname   Specifies the name of the associated configuration block.
              If the menu item is selected from the startup menu, DOS
              carries out the commands in the associated configuration
              block, as well as any commands at the beginning of
              CONFIG.SYS and any commands in the configuration blocks
              with the [COMMON] command header.
  menu_text   Specifies the text you want DOS to display for the menu
              item. If you do not specify any menu text, DOS displays
              the block name as the menu item.

MULTITRACK

DOS 4.0 and above

Specifies whether multitrack disk operations are used or not.

MULTITRACK=ON|OFF
The default setting is MULTITRACK ON.

NUMLOCK

DOS 6.0 and above

Sets or clears Num Lock.

NUMLOCK=ON|OFF

REM

DOS 4.0 and above

Inserts comments.

REM comment

  comment     Specifies a comment.
In DOS 6 and above CONFIG.SYS lines starting with ; are treated as comments.

SET

DOS 6.0 and above

Sets DOS environment variables.

SET variable=string

  variable    Specifies the environment-variable name.
  string      Specifies a series of characters to assign to the variable.

SHELL

DOS 2.0 and above

Loads a command shell.

SHELL=[drive:][path]filename [parameters]

  filename    Specifies the filename of the command shell to load.
  parameters  Specifies the parameters to pass to the command shell.
The default command shell is COMMAND.COM in the root directory of the boot drive.

STACKS

DOS 3.2 and above

Allocates hardware interrupt stacks.

STACKS=n[,m]

  n           Specifies the number of hardware stacks from 8 to 64 or 0.
  m           Specifies the size of each hardware stack from 32 to 512 or 0.
This was called STACK in DOS 3.2 and renamed to STACKS for DOS 3.3 and above.
DOS 3.2 did not allow STACK=0,0 to be specified.
The default setting is STACKS=0,0 for PC and XT systems, STACKS=9,128 for all others.

SUBMENU

DOS 6.0 and above

Specifies a startup submenu item.

SUBMENU=blockname[,menu_text]

  blockname   Specifies the name of the associated submenu block.
  menu_text   Specifies the text you want DOS to display for the submenu
              item. If you do not specify any menu text, DOS displays
              the block name as the submenu item.

SWITCHES

DOS 4.0 and above

Specifies special DOS options.

SWITCHES=[/K][/N][/F][/T][/W]

  /K          Forces an enhanced keyboard to behave like a conventional
              keyboard.
  /N          Prevents you from using the F5 or F8 key to bypass startup
              commands.
  /F          Skips the delay after displaying the "Starting DOS..."
              message during startup.
  /T          Indicates the BIOS time rollover byte is a flag instead
              of a counter.
  /W          Specifies that the WINA20.386 file has been moved to a
              directory other than the root directory.
/T and /W are only available in DOS 5 and above.
/N and /F are only available in DOS 6 and above.

Removed DOS CONFIG.SYS commands

AVAILDEV

DOS 2.x only

Specifies whether device names may be used without the \DEV\ prefix.

AVAILDEV=TRUE|FALSE

  TRUE        \DEV\ is not required for device names.
  FALSE       \DEV\ is required for device names.
The default value is TRUE.
In DOS 3.0 and above this is always true.

CPSW

DOS 4.0x only

Specifies whether code page switching is enabled or not.

CPSW=ON|OFF
This was for proposed code page switching support but the functionality was never publicly implemented.

IFS

DOS 4.0x only

Loads an installable file system (IFS) driver.

IFS=[drive:][path]filename [parameters]

  filename    Specifies the filename of the IFS driver to load.
  parameters  Specifies the parameters to pass to the IFS driver.
In DOS 5.0 and above IFS driver support was removed.

STRING

DOS 3.0 only

Specifies the size of the string substitution buffer for network names.

STRING=n
In DOS 3.1 and above the string substitution buffer was moved out of the DOS data area.

SWITCHAR

DOS 2.x only

Specifies the default switch character.

SWITCHAR=char
The default value is / (slash).
In DOS 3.0 and above this is always /.

DOS 6.0 and above interactive startup notes

[MENU]
Specifies that a startup menu is used. The commands INCLUDE, MENUCOLOR, MENUDEFAULT, MENUITEM and SUBMENU must be within a [MENU] block and only those commands and REM may be used within a [MENU] block.
[COMMON]
Defines a block of commands which are always executed.
[blockname]
Defines a named menu block.
CONFIG environment variable
Set to the selected blockname for use in AUTOEXEC.BAT.
command?=parameters
Specifies that the user should be asked whether to execute the command or not. All commands may use ?= except COMMENT, INCLUDE, MENUCOLOR, MENUDEFAULT, MENUITEM, REM and SUBMENU.
F5
Pressing F5 at startup causes CONFIG.SYS and AUTOEXEC.BAT to be skipped. The /D switch is passed to COMMAND.COM to skip AUTOEXEC.BAT.
F8
Pressing F8 at startup causes CONFIG.SYS and AUTOEXEC.BAT to be interactively executed with prompting. The /Y switch is passed to COMMAND.COM to interactively step through AUTOEXEC.BAT. At the prompt pressing Y will execute the command, N will skip the command, ESC will execute the command and end further prompting, F5 will skip the command and end further processing.