The story was written in TUTOR, the lesson "authoring" language. The language was designed to be easily understood and usable by the average instructor or teacher. It was used by many teachers to write lessons. The TUTOR language also had some additions which made it powerful for graphics and animation.
Some animation was done by drawing and erasing lines or text. Since the terminal had a downloadable character set, a lesson could also draw and erase the characters. That is the case in the code example below.
A "unit" was the name of a segment of code. If you had a series of units, each with some text in them (done with "at" and "write" commands), and nothing more, each press of the -NEXT- key would display each subsequent page of text. It was that easy.
However, a unit could also be called from elsewhere in the lesson, thus being used as a subroutine. That's the case here. Unit "capek" was called from various points in the story. Mike Capek was always displayed in the same spot on the screen, but could with a little more programming, have been displayed anywhere.
"doto" on line 2 is the start of a loop. It starts the variable "inc" at 1 and on each pass of the loop, increments by one until it gets to 3. The loop ends at line 19, where the label "1end" is.
The "at" command tells where to start writing; here it is at line 4, column 4.