The following observations can be made about secretaries, typists, and other non-programmers who have used learn:
It takes an hour or two for a novice to get through the script on file handling. The total time for a reasonably intelligent and motivated novice to proceed from ignorance to a reasonable ability to create new files and manipulate old ones seems to be a few days, with perhaps half of each day spent on the machine.
The normal way of proceeding has been to have students in the same room with someone who knows UNIXand the scripts. Thus the student is not brought to a halt by difficult questions. The burden on the counselor, however, is much lower than that on a teacher of a course. Ideally, the students should be encouraged to proceed with instruction immediately prior to their actual use of the computer. They should exercise the scripts on the same computer and the same kind of terminal that they will later use for their real work, and their first few jobs for the computer should be relatively easy ones. Also, both training and initial work should take place on days when the UNIXhardware and software are working reliably. Rarely is all of this possible, but the closer one comes the better the result. For example, if it is known that the hardware is shaky one day, it is better to attempt to reschedule training for another one. Students are very frustrated by machine downtime; when nothing is happening, it takes some sophistication and experience to distinguish an infinite loop, a slow but functioning program, a program waiting for the user, and a broken machine.*
One disadvantage of training with learn is that students come to depend completely on the CAI system, and do not try to read manuals or use other learning aids. This is unfortunate, not only because of the increased demands for completeness and accuracy of the scripts, but because the scripts do not cover all of the UNIXsystem. New users should have manuals (appropriate for their level) and read them; the scripts ought to be altered to recommend suitable documents and urge students to read them.
There are several other difficulties which are clearly evident. From the student's viewpoint, the most serious is that lessons still crop up which simply can't be passed. Sometimes this is due to poor explanations, but just as often it is some error in the lesson itself -- a botched setup, a missing file, an invalid test for correctness, or some system facility that doesn't work on the local system in the same way it did on the development system. It takes knowledge and a certain healthy arrogance on the part of the user to recognize that the fault is not his or hers, but the script writer's. Permitting the student to get on with the next lesson regardless does alleviate this somewhat, and the logging facilities make it easy to watch for lessons that no one can pass, but it is still a problem.
The biggest problem with the previous learn was speed (or lack thereof) -- it was often excruciatingly slow and made a significant drain on the system. The current version so far does not seem to have that difficulty, although some scripts, notably eqn, are intrinsically slow. eqn, for example, must do a lot of work even to print its introductions, let alone check the student responses, but delay is perceptible in all scripts from time to time.
Another potential problem is that it is possible to break learn inadvertently, by pushing interrupt at the wrong time, or by removing critical files, or any number of similar slips. The defenses against such problems have steadily been improved, to the point where most students should not notice difficulties. Of course, it will always be possible to break learn maliciously, but this is not likely to be a problem.
One area is more fundamental -- some UNIXcommands are sufficiently global in their effect that learn currently does not allow them to be executed at all. The most obvious is cd, which changes to another directory. The prospect of a student who is learning about directories inadvertently moving to some random directory and removing files has deterred us from even writing lessons on cd, but ultimately lessons on such topics probably should be added.