Among the most important library types are vector and string. A string is a variable-length sequence of characters, and a vector is a container of objects of a single type.

Iterators allow indirect access to objects stored in a container. Iterators are used to access and navigate between the elements in strings and vectors.

Arrays and pointers to array elements provide low-level analogs to the vector and string libraries. In general, the library classes should be used in preference to low-level array and pointer alternatives built into the language.