C itself is trivial. But useless. Learning C is like learning to use a scalpel. C is useful in a situation, and what you really need to learn is that situation.

C itself is trivial. But useless. Learning C is like learning to use a scalpel. C is useful in a situation, and what you really need to learn is that situation. Is it microcontrollers? Learn some basic EE, and to read datasheets and to not trust them. Is it low level programming in an OS? Learn about system calls and interfaces offered by the OS. Is it to make an OS? Learn some assembly and hardware insides.