The TeachText reference article from the English Wikipedia on 24-Apr-2004
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TeachText

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The TeachText application is a simple text editor made by Apple Computer that ran on Mac OS 9 and earlier, and now runs only in Mac OS Classic under Mac OS X.

SimpleText evolved from TeachText which was used to distribute Readme documents, which was derived from the Edit application, a simple editing application distributed with the earliest of Macintoshes to demonstrate the use of the Macintosh interface.