My USA college had 3 digit codes. Introduction to computer science was 101. And most people I know of title '101' as the introduction idea. Second year studen

My USA college had 3 digit codes. Introduction to computer science was 101. And most people I know of title '101' as the introduction idea. Second year students take 201, 231, etc. Etc. Third year was 3xx. Fourth year was weird, because you take a few graduate classes. Everything from 4xx standard 4th year stuff, to 6xx or 7xx graduate level stuff was available. ------- I'm pretty sure 6xx or 7xx was more about when the professors felt like teaching btw. A 6xx class was offered every year. 7xx may only be offered once (ever), or maybe every few years at best.