What does symbol # means in #define S(x) (cout<<#x<

Question

#define S(x) (cout<<#x<<endl)

Using # will print whatever string, int, float I place in S(x).
For example:

S(Door Class Default Constructor);

will print

Door Class Default Constructor

I Wasn't able to find any documentation regarding it.
Explain how is it able to do so.

Answer 1

It causes the expanded x to be wrapped in double quoates, "

It's often called the stringize operator and you can find more information here.