What does operator ":" inside a struct mean in C?

Question

I'm working with a piece of code and I come across with something similar to this:

struct {
  int a : 1;
  int b : 1;
};

I don't know what is the function of : 1 here. For your interest, that struct is inside a union which in turn is inside a typedef struct.

Thanks,

Answer 1

This is used to assign value to a bit. You can read about bitfields here.