A ttxt file extension is related to the Apple SimpleText and used for its data files.
TTXT file extension - Apple SimpleText data
What is ttxt file? How to open ttxt files?
The ttxt file extension is associated with Apple SimpleText text editor.
Apple SimpleText was a part of older versions of the Apple Mac OS operating system.
In Mac OS X (macOS), SimpleText is replaced by the more powerful TextEdit, which reads and writes more document formats. Apple has released the source code for a Carbon version of SimpleText in the Panther Developer Tools.
This ttxt file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.