Troubleshooting Erratic Keyboard Behavior in MS-DOS (94008)
The information in this article applies to:
• 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 Q94008
After you install MS-DOS 5.0 or later you may experience keyboard problems.
Use the following procedure to troubleshoot keyboard problems in MS-DOS:
• Add the line SWITCHES=/K to your CONFIG.SYS file.
SWITCHES=/K forces the system to use conventional keyboard
functions rather than the extended keyboard functions.
MS-DOS versions 4.x and later read information from extended or
enhanced (101- and 102-key) keyboards differently than from standard
(84-key) keyboards. This allows MS-DOS to determine information such
as which ENTER key is pressed on enhanced keyboards.
Some older terminate-and-stay-resident (TSR) programs that hook into
the keyboard interrupt don't recognize there are two ways to read from
enhanced keyboards. In MS-DOS 4.x and later, it is possible for TSRs
(and other applications) to fail because of how MS-DOS reads from
• If you are using ANSI.SYS in the CONFIG.SYS file, add the /K
parameter. For example:
This has the same effect as step 1. The /K switch must be used in
both places if you are loading ANSI.SYS.
• Load KEYB.COM.
At the command prompt type the following:
If this corrects the problem, add the command to your AUTOEXEC.BAT
file after the PATH statement.
• Test HIMEM.SYS.
If you are using HIMEM.SYS, remove this device driver to determine if
the problem is being caused by the A20 handler. If it is, add the
switch /cpuclock:on to the DEVICE=C:\DOS\HIMEM.SYS line in your
CONFIG.SYS file, or test different machine switches. For more
information about machine switches, see the section titled "You
receive a message that HIMEM.SYS is missing or not loaded" in Chapter
9 of the "MS-DOS User's Guide and Reference" for version 5.0. If you
are using MS-DOS 6 or 6.2, type "help himem" (without the quotation
marks) at the MS-DOS command prompt and then press ENTER.
If your computer is not on the list of machines, you are not sure
which number to use, or the machine number for your computer
doesn't correct the problem, try these machine numbers in the
following order: 1, 11, 12, 13, 8, 2-10, 14-16.
• Check the BIOS.
If the manufacturer is AMI and the last two digits of the serial
number are K7, the BIOS can cause problems with the keyboard in
Windows and on networks. An upgrade to K8 may correct the problem.
Some of the products included here are manufactured by vendors independent
of Microsoft; we make no warranty, implied or otherwise, regarding these
products' performance or reliability.
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