PAUSE (CONFIG.SYS directive)

CONFIG.SYS
Company type	Configuration file
Industry	Operating systems
Founded	1983 (with DOS version 2.0)
Products	Configuration instructions for DOS and OS/2

Adapted from the English Wikipedia article PAUSE (CONFIG.SYS directive), available under CC BY-SA 4.0Updated 9 August 2025

CONFIG.SYS serves as the chief configuration file for DOS and OS/2 operating systems. This plain text file, written in ASCII, holds setup instructions accessible to users, which the system's DOS BIOS—typically found in IBMBIO.COM or IO.SYS—interprets during the startup process. CONFIG.SYS first appeared with DOS version 2.0.

Usage

The directives within CONFIG.SYS tailor DOS to manage devices, software, and memory allocation. Once CONFIG.SYS has been processed, DOS initiates the command interpreter designated by the SHELL directive; if none is specified, it defaults to COMMAND.COM, which then executes the commands in AUTOEXEC.BAT.

CONFIG.SYS predominantly contains name=value pairs that define settings or load components such as device drivers and terminate-and-stay-resident programs (TSRs). This file is located in the root directory of the bootable drive.

The same filename is also utilized by (DCP), an MS-DOS variant developed by East-German manufacturer VEB Robotron.

Certain DOS derivatives search for alternative filenames that take priority over CONFIG.SYS:

- Advanced editions of Concurrent DOS 386, Concurrent DOS XM, Multiuser DOS, System Manager, and REAL/32 replace CONFIG.SYS with CCONFIG.SYS or CCONFIG.INI (in Multiuser DOS), storing extra configuration data within CCONFIG.BIN, which can be modified using CONFIG.EXE.

- In systems like DR DOS 3.31, PalmDOS 1.0, Novell DOS 7, OpenDOS 7.01, and DR-DOS versions 7.02 and later, DCONFIG.SYS is checked first to facilitate multi-boot environments and disk compression situations where boot drive letters might vary.

- Additionally, OpenDOS 7.01 and DR-OpenDOS 7.02 verify the presence of ODCONFIG.SYS, while some DR-DOS releases from version 7.02 onward also look for DRCONFIG.SYS.

Starting with DR DOS 6.0, the command SYS /DR:ext allows changing system file extensions to support multiple configurations running side-by-side under boot managers like LOADER. The SHELL command supports specifying alternative AUTOEXEC.BAT files via /P[:filename.ext], and in this mode, COMMAND.COM can execute files with extensions other than .BAT; this functionality is also available in 4DOS. The CHAIN=filespec directive permits continued processing of additional configuration files located outside the root directory, with optional label selection introduced in DR-DOS 7.02 and later.

From DR-DOS 7.03 onward, a SYS /A option was introduced to copy CONFIG.SYS and AUTOEXEC.BAT alongside system files.

In other environments, FreeDOS employs FDCONFIG.SYS, while from version 7.24 onward, RxDOS uses RXCONFIG.SYS. The operating system PTS-DOS uses a configuration file named CONFIG.PTS.

Both CONFIG.SYS and AUTOEXEC.BAT exist in the root directory of Windows 95 and Windows 98 boot partitions but are generally left empty. In contrast, Windows Me does not process CONFIG.SYS during startup; instead, it retrieves environment settings from the Windows Registry.

Within the context of FlexOS, CONFIG.SYS is a binary file that specifies resource managers along with device drivers.

Example

A sample CONFIG.SYS configuration 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>

:;*?!

: Establishes labels within CONFIG.SYS to serve as jump destinations for , , , , and .
: Functions similarly to , also utilized for inline comments. (MS-DOS/PC DOS treats quoted inline comments differently.)
: Alternative syntax for initiating inline comments.
: Prompts Yes/No confirmations before executing subsequent directives. FreeDOS supports conditional logic with boot menus but lacks optional message prompts. DOS 6.0 and later provide a comparable feature by appending after commands (e.g., ).
: Executes the following directive without condition.

ATemplate:NbndC

: Determines program termination behavior upon encountering errors.
: Sets file access date stamping on FAT file systems.
: Enables conditional execution on AT-compatible hardware.
: Boot manager utility.
: Adjusts verbosity level of error messages.
: Alters default serial driver assigned to the AUX device.
: Restricts access to character devices outside the phantom \DEV directory.
: Loads a base device driver into memory.
: Triggers system beep regardless of notification settings.
: Defines the next operating system to boot.
: Enables or disables extended Ctrl+C interrupt checking.
: Specifies the number of disk buffers to allocate.
: Loads disk buffers into High Memory Area (HMA) or Upper Memory Blocks (UMB).
, , (Embedded DOS 6-XL exclusive): Configure cache block allocation and flushing intervals.
: Executes programs within CONFIG.SYS, pausing processing until program completion.
: Sets Caps Lock key status at startup.
, (PTS-DOS only): Defines CD-ROM driver name and buffer quantity.
: Continues processing of CONFIG.SYS from another file or label.
, , and other system directives primarily found in PTS-DOS or DR-DOS versions manage hardware configurations and display behavior to optimize system performance.

COM Ports and Device Settings

Directives named COM1 through COM4 specify configuration details such as quantity, logical ordering, I/O port addresses, and timeout values for serial ports, mainly supported in DR-DOS 7.02 and later. Additional directives like AUX modify default serial device drivers.

Commenting and International Support

The COMMENT directive allows redefining inline comment characters or ignoring lines across different DOS variants, while COUNTRY activates internationalization features throughout DOS systems.

CPU-Specific Execution

Directives including CPU88, CPU86, CPU286, CPU386, CPU486, along with their variants, facilitate conditional execution based on processor type and generation, enabling hardware-optimized configurations tailored to specific CPUs.

This focused collection of CONFIG.SYS commands provides meticulous control over system startup procedures, device handling, and hardware-specific settings essential for fine-tuning legacy DOS environments in business contexts that demand customized boot sequences and resource management.

DTemplate:NbndF

: Alters relocation settings for drive descriptor tables.
: Defines memory segment address used for multi-sector disk data deblocking operations.
: Activates internal debugger support.
: Boot manager component.
: Loads device drivers into conventional memory.
: Loads device drivers into upper memory blocks (equivalent to in DRDOS 5.0).
: Sets country code and codepage for keyboard, screen, and printer devices.
: Configures cache memory size parameters.
: Specifies floppy disk compatibility mode settings.
: Selects display font used by the system.
: Controls loading of DOS into high memory and upper memory areas.
: Loads DOS data tables (BUFFERS, FCBS, FILES, LASTDRIVE, STACKS) into upper memory space.
: Indicates an alternative directory path for DOS files.

: Specifies search paths for data files during operation.
: Defines physical characteristics of disk drives.
: Sets parameters for drives not recognized by the system.
: See .
: Enables drive support for PDUMP.nnn error log files.
: Displays messages on screen during processing.
: Displays messages including ANSI escape sequences on screen.
: Enables additional integrity checks when launching programs.
: Sets expected error or return codes from executed programs.
: Configures A20 gate state when starting applications.
: Terminates CONFIG.SYS processing prematurely except for SWITCHES and SHELL commands.
: Defines hash table size used to speed up file opening operations (distinct from MS-DOS/PC DOS FASTOPEN).
: Specifies number of cached File Control Blocks open simultaneously (shares buffer with FILES under DR-DOS).
: Similar to FCBS but explicitly loaded into upper memory area.
: Boot manager function.
: Sets maximum number of concurrently open files allowed by the system.
: Equivalent to FILES but loads file handles explicitly into upper memory space.
: Includes specified CONFIG.SYS subsections during execution (see IGNORE).

GTemplate:NbndI

: Awaits a key press or timeout, then assigns the error level to the ASCII value of the key or 1024 if timed out.
: Resumes processing of CONFIG.SYS at a given label.
: Continues nested CONFIG.SYS processing at a specified label and returns control to the previous point.
: Refer to , , or for additional details.
: Consult for further information.
: See for related functionality.
: Refer to or for more context.
: See or for related commands.
: Consult for additional guidance.
: Loads a terminate-and-stay-resident (TSR) program into memory after relocating the DOS data segment. Compare with INSTCDEX.
: Refer to , , or for further reference.
: See for related instructions.
: Consult or for additional information.
: Activates console and command line history buffer with advanced pattern search capabilities.
: Defines the address of the High Memory Area (HMA) segment.
: Sets up HLT (halt) mode for power saving.
: Enables scanning for boot sector viruses.
: Loads file systems that can be installed dynamically.
: Prevents execution of certain CONFIG.SYS subsections.
: Permits selected applications to operate at ring 2, allowing direct hardware I/O access.
: Includes directives from another menu block, emulated via GOSUB/RETURN in DR-DOS environments.
: Sets the status of keyboard Insert mode.
: Installs TSR programs into conventional memory.
: Loads TSR programs into upper memory areas (similar to HIINSTALL in DR DOS 5.0).
: Installs TSR programs following relocation of the DOS data segment. Compare with INSTCDEX.
: Adjusts PIC interrupt priorities by assigning the highest priority to a specified IRQ number.

KTemplate:NbndM

: Defines the keyboard layout configuration.
: Indicates the relocated keyboard buffer's memory address.
: Sets the limit on accessible drive letters.
: Functions like LASTDRIVE but loads the Current Directory Structure (CDS) into upper memory instead.
: Specifies paths for searching dynamic link libraries (DLLs).
: Controls compatibility handling for legacy software.
: Determines the number of allowable file locks.
: Configures boot logo display when using PTS-DOS boot manager.
: Sets parameters including count, order, I/O address, and timeout for LPT1 port devices.
: Defines similar parameters as above for LPT2 port devices.
: Specifies count, order, I/O address, and timeout settings for LPT3 devices.
: Enables and configures settings for LPT4 devices.
: Sets wait duration before increasing process priority levels.
: Controls strategy for memory allocation management.
: Specifies default method used by DOS for allocating memory.
: Defines options available within menus.
: Sets color schemes for menus (can be emulated under DR-DOS).
: Specifies which menu block is default (emulatable in DR-DOS).
: Defines individual menu blocks (emulated under DR-DOS).
: Enables or disables operations involving multiple disk tracks simultaneously.
: Continues processing of CONFIG.SYS in a new file after loading a device driver and setting the %NEWFILE% environment variable.

NTemplate:NbndQ

: Sets the default "No" character used in Yes/No/Resume prompts.
: Controls whether the keyboard Num Lock state is turned on or off at startup.
: Enables conditional execution based on the previous error code, e.g., .
: Shows text and waits for a keypress, functioning similarly to and in DR-DOS systems.
: Requires user confirmation upon encountering errors in CONFIG.SYS processing.
: Configures buffer sizes allocated to LPT parallel ports.
: Executes commands conditionally only on PC-compatible hardware platforms.
: Sets process scheduler priority levels.
: Assigns priority levels specifically for disk I/O operations programs.
: Changes default printer device driver from LPT1 to LPT3 or LPT4 as specified.
: Determines whether DOS applications are allowed to run under current settings.
: Loads a user interface shell environment during startup.
: Executes commands conditionally on IBM PS/1-compatible machines only.
: Executes commands conditionally on IBM PS/2-compatible machines only.
: Suppresses output display sent to STDOUT.

RTemplate:NbndT

: Activates automatic system reboot when errors occur.
: Permits inclusion of comments within CONFIG.SYS files.
: Allocates a drive letter for local block device drivers.
: Defines the default character for Resume () prompts in Yes/No/Resume queries.
: Returns control from nested CONFIG.SYS processing to the previous GOSUB or SWITCH command with an optional return value.
: Specifies the size of real mode memory available.
: Executes programs in CONFIG.SYS simultaneously in the background, functioning similarly to CALL or INSTALL commands in DOS.
: Saves the initial character of deleted files within the FAT reserved space.
: Determines the video mode under FreeDOS or selects screen access methods for PTS-DOS.
: Sets the keyboard’s Scroll Lock key state to either on or off.
: Establishes environment variables for system use.
: Loads the command interpreter shell.
: Initiates the shell with an optional size parameter to relocate it into HMA or UMBs, thereby minimizing memory fragmentation.
: Defines keyboard modifier states such as Shift Lock, Num Lock, Scroll Lock, and Insert mode.
: Controls whether files close automatically upon a Ctrl+Alt+Del event.
: Bypasses the Power-On Self-Test (POST) during system reboot.
, STACKSIZE, STACKSHIGH: Manage stack sizes and quantities across different DOS versions, important for handling hardware interrupts and memory allocation.
, SYSBOOT, SYSGEN, SYSLOAD: PTS-DOS-specific boot manager options that dictate system loading locations and support for alternate operating system booting.
(DOS 6.0+) Allows definition of submenu blocks, although this feature is not natively supported by DR-DOS or FreeDOS.
, SWAPPATH, THREADS, TIMESLICE: Exclusive to OS/2, these parameters manage error log suppression, swap file directory paths, thread concurrency levels, and scheduler time slice durations respectively.
, SWITCHES: Provide conditional processing within CONFIG.SYS files in DR DOS and Novell DOS environments, enabling dynamic configuration based on user selections or command-line switches.
, TMPEXT: Sets the default system switch character (either '/' or '-') and defines temporary file extensions in PTS-DOS.
, TRACEBUF: Enables or disables single-step execution of CONFIG.SYS while specifying log buffer sizes, with variations between DOS and OS/2 implementations.
(OS/2 3.0+) Captures detailed error logs for advanced diagnostic purposes.

This section details essential configuration directives used across multiple DOS variants—including DR-DOS, PTS-DOS, FreeDOS, Novell DOS, and OS/2—offering enterprises granular control over boot procedures, environment variables, device priorities, error management, and system resources crucial for maintaining and optimizing legacy computing environments.

UTemplate:NbndZ

: Assigns a specific memory segment to function as an Upper Memory Block (UMB) in DOS.
: Configures parameters for the UMB server functionality.
: Defines address ranges designated as UMB RAM areas.
: Enables or disables verification of disk writes to ensure data integrity.
: Specifies the reported version number of DOS to applications or utilities.
: Manages VGA display status settings.
: Sets the active video mode currently in use by the system.
: Enables virtual DMA (Direct Memory Access) capabilities for enhanced performance.
: Controls processor features related to Virtual Mode Extensions (VME).
: Configures Virtual Device Driver (VxD) settings tailored for Windows environments.
: Establishes system-level support parameters for Windows operating systems.
: Adjusts relocation settings for the Extended BIOS Data Area (EBDA).
: Allows conditional execution based on compatibility with XT-class machines.
: Implements built-in support mechanisms addressing Year 2000 (Y2K) compliance issues.
: Defines the default character used to signify "Yes" in prompt dialogs.
: Manages tracking options related to file deletion activities.

Issues

Although the system is capable of booting without CONFIG.SYS or AUTOEXEC.BAT, these files are crucial for comprehensive startup customization and meeting software prerequisites. Any corruption or absence of these files requires diagnostic efforts.

In cases where CONFIG.SYS does not contain a SHELL directive or if it is damaged or missing, DOS attempts to locate COMMAND.COM in the root directory of the boot drive. Versions prior to 6.0 will fail to boot if COMMAND.COM is not found, whereas MS-DOS 6.0, PC DOS 6.1, and Novell DOS 7 and later will prompt the user to specify a command processor path. This prompt also appears if the main shell terminates unexpectedly or is exited intentionally, enabling replacement of the command shell during runtime without rebooting.

The COMMAND.COM from MS-DOS 7.0 and later is not compatible with DR-DOS, which commonly resides in C:\ within dual-boot configurations. As a result, DR-DOS versions 7.02 and above enforce SHELL directives when operating in skip, trace, or step modes, requiring users to provide a valid shell before launching COMMAND.COM if none is detected.

The size of CONFIG.SYS is restricted to a few kilobytes under MS-DOS and PC DOS (up to 64 KB in newer releases), while DR-DOS imposes no fixed limit aside from filesystem constraints. MS-DOS processes CONFIG.SYS by tokenizing its contents and sorting directives by category—loading device drivers first—whereas DR-DOS parses CONFIG.SYS sequentially line-by-line. This approach grants precise control over load order and enables conditional execution based on hardware presence or user input.

Thanks to its line-by-line parsing, DR-DOS can integrate temporary external utilities through the INSTALL command, providing enhanced flexibility for managing drivers and TSR programs.

The maximum length for a SHELL directive increased from 31 characters in MS-DOS/PC DOS versions 2.0 through 4.01 to 128 characters in subsequent editions; DR-DOS supports up to 255 characters. It should be noted that CONFIG.SYS directives do not accommodate long filenames.

Dual booting DOS and Windows 9x

When Windows 95 is installed over an existing DOS or Windows environment, the original CONFIG.SYS and AUTOEXEC.BAT files are renamed to CONFIG.DOS and AUTOEXEC.DOS respectively, facilitating dual-boot operations between Windows 9x and DOS. Upon booting into DOS mode, these backup files are temporarily restored as CONFIG.SYS and AUTOEXEC.BAT. Additionally, Windows 95 system files are saved under the names CONFIG.W40 and AUTOEXEC.W40.

In configurations where Caldera DR-DOS versions 7.02 or 7.03 coexist with Windows 95, the Windows CONFIG.SYS and AUTOEXEC.BAT remain unchanged, while DR-DOS uses alternative startup filenames: DCONFIG.SYS and AUTODOS7.BAT.

OS/2 / Windows NT

OS/2 heavily relies on CONFIG.SYS for driver setup and environment configuration prior to loading its graphical interface. Within the OS/2 subsystem of Windows NT, what appears as CONFIG.SYS to OS/2 applications is actually maintained within the system registry.

A variety of undocumented directives exist within OS/2's CONFIG.SYS implementation. The use of CONFIG.SYS continues in OS/2 derivatives such as eComStation and ArcaOS.

External links

Information on AUTOEXEC.BAT and CONFIG.SYS at Computer Hope
Overview of Windows 98 / MS-DOS 7.10 CONFIG.SYS directives (archived)
Caldera’s CONFIG.SYS Command Reference (archived) – summary of DR-DOS 7 directives
Documentation of FreeDOS CONFIG.SYS directives
PTS-DOS 2000 Pro User Manual including CONFIG.SYS directives overview
Unofficial German FAQ for PTS-DOS (PTS/FAQD) containing additional CONFIG.SYS directives