Accepting Keyboard Input in Batch Files (77457)

The information in this article applies to:
    Microsoft MS-DOS operating system 3.1
    Microsoft MS-DOS operating system 3.2
    Microsoft MS-DOS operating system 3.21
    Microsoft MS-DOS operating system 3.3
    Microsoft MS-DOS operating system 3.3a
    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 Q77457


The MS-DOS batch language facility does not provide a means for you to provide input to control program flow. All information input from you must be entered from the command line.

By using a short program created with the MS-DOS Debug utility, you can provide information at the time of batch file execution.

NOTE: Although the Debug program works with MS-DOS 6.0 or 6.2, it is not required. If you are using MS-DOS 6.0 or 6.2, type help choice at the MS-DOS command prompt for more information.


The Debug program at the end of this article will wait for you to input a character from the keyboard and set the value of "errorlevel" equal to the ASCII code value of the character entered. For a list of ASCII characters and their associated values, see the ANSI.SYS section in your MS-DOS manual.

Most keyboard characters are represented by only one code. However, the functions and ALT key combinations send two codes: a zero, followed by another code. The REPLY.COM program will set "errorlevel" equal to the second code passed. For example, the F8 key sends a zero followed by the value 66. This will be interpreted by REPLY.COM as the character "B," which has an ASCII value of 66.

REPLY.COM can be used within batch files to allow user input to control the flow of the program. For example, the following AUTOEXEC.BAT file allows you to determine whether or not to install a mouse driver during startup:
   @Echo off
   Echo Install Mouse Driver (y/n)?
   If errorlevel 121 if not errorlevel 122 goto install
   If errorlevel 89 if not errorlevel 90 goto install
   If errorlevel 110 if not errorlevel 111 goto NoMouse
   If errorlevel 78 if not errorlevel 79 goto NoMouse
   goto ask
For more information about using the "errorlevel" environment variable, query on the following word in the Microsoft Knowledge Base:



To create REPLY.COM, enter the text listed in the Instruction column. Press ENTER after each instruction. Do not enter the text listed in the Comment column; it is for your reference.
           Instruction     Comment
           -----------     -------

            DEBUG       Executes MS-DOS DEBUG utility
-A 100                  Begin assembling instructions at memory location
xxxx:0100   MOV AH,08   Get character input without echo
xxxx:0102   INT 21      Perform MS-DOS service
xxxx:0104   CMP AL,0    Compare AL with zero
xxxx:0106   JNZ 010A    If lead zero, get second code of character
xxxx:0108   INT 21      Perform MS-DOS service
xxxx:010A   MOV AH,4C   Terminate process with return code
xxxx:010C   INT 21      Perform MS-DOS service
xxxx:010E   <ENTER>
CX 0000
Writing 000E bytes


"Supercharging MS-DOS," pages 97-98, by Van Wolverton, Microsoft Press, 1989, 1991 (Updated for Version 4).

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB77457