My first C class had Gameboy programming. There were no libraries to include, and most of the data manipulation was around scores and drawing pixels.

My second C class went into mutexes and things (producers & consumers of some data)

My third class that used C had kernel modules. Our kernel module project was to write a model of a parking lot. There was some user code that called our module saying whether it was a normal vehicle, a handicap vehicle, or an emergency vehicle. The parking lot also had 2 states, emergency or normal. In an emergency, only emergency vehicles could come in, everything else was rejected. The code ran with M floors and N parking spaces per floor, and returned the lowest floor in which you could park.

We also wrote an identical piece of userspace code, and compared how fast each performed.

He may possibly be referring to just getting familiar with C, since there is a lot of stuff you must worry about with C that you may not be used to with higher level languages (such as having to manually manage your memory allocates, etc).