A vector container class generalizes the concept of an ordinary C array. As an array, a vector is an indexed data structure, with index values that range starts from 0 to one less than the number of elements covered in the structure. Like an array, values are most commonly assigned to and extracted from the vector using a subscript operator. However, vector differs from an array in the following important respects:

The size of the vector can be changed dynamically. New elements may be added on to the end of a vector, or into the middle. It is important to note, as these abilities are provided; insertion into the middle of a vector is not as capable as insertion into the middle of a list.