Interestingly, PLATO was successful in narrow areas of work and in strange ways. The airlines adopted it for pilot training. I don't know whether those programs/lessons are still in use today. The military used it, especially the Navy. And there was a wonderful real time (and quite costly) emergency room simulator for training medical technicians. That was from Canada and I can't find the link at the moment. The elementary math lessons were amazing-- kids thought they were games but they taught serious arithmetic skills. There was a wonderful chemical titration lab simulation, great physics lessons by Bruce Sherwood, and many many other terrific pieces of "courseware" or "lessonware" as it was called at the time. Unfortunately, too many people used PLATO to develop bad courseware. Equally unfortunate, bad software and courseware is still all too common. Aside: ever encounter a long, seemingly endless and unstoppable flash animation before you can get to a site or web page? Well, unfortunately, that also got its start with PLATO. LOL.

The abrupt "no" response was a system default that programmers were expected to anticipate and correct. PLATO, in fact, had a very rich set of possible responses based on system variables set by the student reponse. But a lot of authors had no idea how the system worked or what its potential power was so it was the usual garbage in and garbage out just as so many computer-based teaching programs are today! Sadly. Properly programmed lessons would parse and process a student response, give appropriate correction and feedback, provide several levels of HELP, and the system used automatic spelling checks and markups. The problems came from inexperienced authors, not from the system software which was brilliantly conceived and amazingly well executed by highly talented people who made it happen with incredibly primitive hardware by today's standards. It was a lot like NASA's moonlanding computers. They did an amazing job for their minimal specifications.