There is a general agreement that the windows-based user interface that was invented by Xerox, adapted by Apple and then stolen by Microsoft was a huge improvement vis-a-vis the cursor and text-based user interfaces of earlier computers.
Nowadays most people take the use of the mouse and idea of gathering files in folders as obvious. It was not.
During my days as a young civil servant in the Norwegian Ministry of Education, Research and Church Affairs (don’t ask!) in the early 1990’s I became one of the local “PC user helpers” and was given the task of explaining the concept of files and folders to people who had no idea of how a computer worked.
I remember that i found a card box and put paper-folders and paper sheet into those folder to illustrate the concepts of the hard drive (the box), the folder (the folder) and the paper sheet (the file).
If I didn’t many of them would just hit the save button, having no idea about where the file went. They were not stupid, but no one had explained to them the basic concepts of computing.
Very few user interfaces are obvious. The uses of a water basin tap, a radio volume button, or a screw driver are all learned behavior.
Anyone who have been to one of the modern “designer hotels” know this, as they suddenly find themselves unable to turn off the lights (where is that light switch?) or get running water in the shower (what button to push or turn, and which way?)
Here is a very funny video from the Norwegian Broadcasting Corporation that describes this dilemma in a wonderful way. It is taken from the show “Øystein og jeg” from 2001. Øystein Backe plays the helper from the help desk and Rune Gokstad is a desperate monk trying to understand how to use — a book! There are English subtitles.
(By the way, the book was not introduced in the Middle Ages, but in late antiquity.)