Language C++

_What does it mean if we write using namespace std?

_Given an integer variable bar. How can you create a pointer foo to bar? How can you extract the integer from the pointer foo? And, what is this called? _How are pointers and arrays related? _Given an array double arr[3] = {1.2, 1.3, 1.4}: If double y = arr[1] and one executes y += 0.4, what is now the value of arr[1]? If double &z = arr[2] and one executes z += 0.4, what is now the value of arr[2]?

Thank you!