Quick Basic has the WIDTH statement which you can use to set the number of character columns and rows for a given screen mode. As to my question: I want to set the number of rows to 60 using the standard VGA graphics mode. Something you can do in Quick Basic as follows:

WIDTH , 60
However, I would like to know what the WIDTH statement is doing on a low level to set the number of rows. The closest piece of information I could find on the subject is: