Can't functions be nested in C?

Question

C++ / C#

I'm reading a textbook from someone Batur on C:


It says that functions cannot be nested, is it true?

Answer 1

According to the language standards, they can't. But there are extensions (in particular, for gcc) that allow you to define functions nested in other functions.
What for? Nested functions are lambdas, which were before C++ lambdas.