“std::endl” vs “\n”

Question

Many C++ books contain example code like this...

std::cout << \"Test line\" << std::endl;

...so I\'ve always done that too. But

Answer 1

There's another function call implied in there if you're going to use std::endl

a) std::cout << "Hello\n";
b) std::cout << "Hello" << std::endl;

a) calls operator << once.
b) calls operator << twice.