Element access

 Element access:

1. reference operator [g] – Returns a reference to the element at position ‘g’ in the vector
2. at(g) – Returns a reference to the element at position ‘g’ in the vector
3. front() – Returns a reference to the first element in the vector
4. back() – Returns a reference to the last element in the vector
5. data() – Returns a direct pointer to the memory array used internally by the vector to store its owned elements.