What does '<<' mean in C?

Question

what does this mean?

#define WS_RECURSIVE    (1 << 0)

I understand that it will define WS_Recursive (1 << 0) but w

Answer 1

It's a bit shift. (1 << 1) is 2 and (1 << 2) is 4. (1 << 0) is 1, which is rather silly, but at least it's precomputed at compile time.