I'm going to ask you to think back to your college days. For some of us that is a greater challenge than others. Courses were listed in the registration catalog with numbers indicating their degree of difficulty. The course numbers seemed to be universally coded the same, such as 101, 201, 301, etc.

The code number "101" was typically reserved for the introductory class. So if you were a freshman enrolling in your first college algebra class, you typically would choose the 101 course to ground yourself in the basics before taking more advanced classes.