What exactly gets stored when referencing external contracts?

Question

Imagine two contracts, A and B

contract A{
    ...
}

contract B{
  A a;
  function B(address aAddr){
     a = A(aAddr);
  }
}

What exactly is B storing about contract A? Does it store function hashes? Does it store A's bytecode?

Answer 1

it creates an instance of A so it is using only a reference in other words B is storing the A's Address, no bytecode no hash.

try to debug the code and watch storage and memory changement. in this exemple the A address is : 0x692a70d2e424a56d2c6c27 aa97d1a86395877b3a