[jwstarr]

The author of TECO, Dan Murphy, wrote an article about its history for the IEEE Annals of the History of Computing. A PDF copy of the article is available here: https://opost.com/tenex/anhc-31-4-anec.pdf

Alas, it does not discuss the gap buffer.

The book The Craft of Text Editing claims the gap buffer technique was first used by TECO (http://www.finseth.com/craft/#c6.6), although this claim is given no support.

[gumby]

Thanks for that reference — I’d never seen it. I’ll be happy never to write any more TECO in my life, but that doesn’t mean I’m not interested.