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

The << operator shifts the left-hand value left by the (right-hand value) bits. Your example does nothing! 1 shifted 0 bits to the left is still 1. However, 1 << 1 is 2, 1 << 2 is 4, etc. Is WS_RECURSIVE a flag in a bitfield?