std::vector has a whole family of member functions concerned with adding and deleting elements. These member functions aren't present in std::array because std::array isn't resizable; but they are present in most of the other containers we're going to be talking about in this chapter. So it's a good idea to get familiar with them now.
Let's start with the two primitive operations specific to vector itself: .resize() and .reserve().
vec.reserve(c) updates the capacity of the vector--it "reserves" space for as many as c elements (total) in the underlying array. If c <= vec.capacity() then nothing happens; but if c > vec.capacity() then the vector will have to reallocate its underlying array. Reallocation follows an algorithm ...
