IMPACT is a port of Levy-Knuth CTangle 3.1 to the Macintosh. It differs from previous ports in two major ways. First, it runs persistently, by which I mean that you can tangle as many files as you like, instead of having to restart the application for each run. Second, it responds to the 'odoc' Apple Event, so you can tangle a file from any other application, for instance, your editor, that will send an appropriate Apple Event. Version 1.1 incorporates some important improvements. A. An options menu allows control over two features. You can specify the file extension used for the output file. For instance, I change this to ``.cp'' when generating C++ files. And you can instruct Tangle to omit all line and section references. The line references seriously confuse the Symantec C++ compiler and debugger. B. Tangle has been revised to create temporary files, rather than replacing the previous versions of its output. Impact then compares the new versions with the previous ones to see if any changes have been made. Only if a file has changed is it replaced. This feature frees a writer to include as many output files as he likes in one web file, without paying the penalty of unnecessary compilations. Messageware. Timothy Larkin PO Box 107 Brooktondale, NY 14817-0107 607.539.7299 tsl1@cornell.edu