The ## operator in C

Question

What does ## do in C?

Example:

typedef struct
{
    unsigned int bit0:1;
    unsigned int bit1:1;
    unsigned int bit2:1;
    unsigned          


        

Answer 1

It is string concatenation, as part of the preprocessor macro.

(In this context, "string" refers to a preprocessor token of course, or a "string of source code", and not a C-string.)