The appearance of the GUI
Historically, in the 60s there was no graphical interface, so far, everything was based on punched cards, if not, perforated paper with algorithms and alphabets and the output was done by printers. There was no interaction with the user.
In 1962, Ivan Sutherland (was born in 1938, and he still alive until today) created in his PhD thesis at Massachusetts Institute of Technology (MIT) the thing we could say: "The first Graphic User Interface ever". Called Sketchpad, this software was the predecessor of the Computer-Aided Drafting (CAD) and opened the doors to the user interface world.
The Sketchpad according to Wikipedia, using a simple interface but intuitive given the user a new experience about "operate a computer". With the touch sensitive monitor of the light pen, the user can "click" in specific regions where they designed for the options. The clickable areas were recognized in touch screen, and the terminal determines whether the area in a XY axis performed some action. Additionally, the user could draw on the screen with a Light Pen (something like a mouse today).