The pages on this site contain documentation for very old MS-DOS software,
purely for historical purposes.
If you're looking for up-to-date documentation, particularly for programming,
you should not rely on the information found here, as it will be woefully
out of date.
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:nCannot Set Tabs Notification
An ASCII file that contains tabs is currently loaded in
memory, so you can't use the Display Command's Tab Stops
Option to change the value of a tab stop.
Unload the ASCII file, then change the Tab Stops option.