Rebooting from Within a Batch File (67929)

The information in this article applies to:
    Microsoft MS-DOS operating system 3.3
    Microsoft MS-DOS operating system 4.0
    Microsoft MS-DOS operating system 4.01
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q67929


The MS-DOS batch language does not provide a means of restarting a system. However, it is possible to restart a system from within a batch file by calling an executable program that performs the task.

NOTE: This article provides instructions that you can use to create the REBOOT.COM file. These instructions have not been tested on all hardware configurations, and are provided "as is" with no warranty stated or implied.


The executable file can be created using DEBUG as follows:

    Start DEBUG by typing the following at the MS-DOS command prompt:


    At the dash prompt, enter the following sequence of commands, each followed by pressing ENTER. (Comments are preceded by ";".)
       A 100                     ; Debug instruction for assemble
       MOV AH,0D                 ; Disk Reset
       INT 21h                   ; causes SmartDrv 4.x to write cache
       MOV AX, 40                ; set up segment addressing
       MOV DS, AX
       OR  BYTE PTR    [17],0C   ; equivalent of pressing CTRL+ALT
       MOV AX,4F53               ; Issue a "DEL" (53h = DEL scan code)
       INT 15h                   ; EMM386 sees this & shuts down
       MOV WORD PTR [72],1234    ; Set REBOOT flag to Warm-Boot (0=cold)
       JMP F000:FFF0             ; Execute the internal restart routine
       <CR>                      ; This line must be blank (just hit ENTER)
       R CX
       20                        ; File size to be written to disk (in hex)
       N REBOOT.COM              ; Filename
       W                         ; Write the file to disk
       Q                         ; Quit Debug
NOTE: The REBOOT.COM file created with this debug script is compatible with SMARTDrive and its write-behind cache feature. The instructions in REBOOT.COM cause SMARTDrive to write (flush) its write-behind cache to disk before the computer is rebooted.

This procedure creates the file REBOOT.COM in the current directory. At this point, you can call the file in the same manner as any other executable file, either from the command line or within a batch file, and the system will reboot.

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB67929