Many programmers claim that they know S. Well, he has the most famous syntax, it has existed for 44 years and it is not littered with incomprehensible functions. He is simple!
I mean, just to say that you know C. Probably you studied it at the institute or along the way, most likely you have some experience in using it, you probably think you know it far and wide, because there is not much you need to know. Actually a lot. With not so simple.