cppreference.com > C++ Iterators ### C++ Iterators Iterators are used to access members of the container classes, and can be used in a similar manner to pointers. For example, one might use an iterator to step through the elements of a vector. There are several different types of iterators:
Iterator | Description
--- | ---
input_iterator | Read values with forward movement. These can be incremented, compared, and dereferenced.
output_iterator | Write values with forward movement. These can be incremented and dereferenced.
forward_iterator | Read or write values with forward movement. These combine the functionality of input and output iterators with the ability to store the iterators value.
bidirectional_iterator | Read and write values with forward and backward movement. These are like the forward iterators, but you can increment and decrement them.
random_iterator | Read and write values with random access. These are the most powerful iterators, combining the functionality of bidirectional iterators with the ability to do pointer arithmetic and pointer comparisons.
reverse_iterator | Either a random iterator or a bidirectional iterator that moves in reverse direction.
Each of the container classes is associated with a type of iterator, and each of the STL algorithms uses a certain type of iterator. For example, vectors are associated with random-access iterators, which means that they can use algorithms that require random access. Since random-access iterators encompass all of the characteristics of the other iterators, vectors can use algorithms designed for other iterators as well. The following code creates and uses an iterator with a vector:
      vector<int> the_vector;
      vector<int>::iterator the_iterator;
      for( int i=0; i < 10; i++ )
        the_vector.push_back(i);
      int total = 0;
      the_iterator = the_vector.begin();
      while( the_iterator != the_vector.end() ) {
        total += *the_iterator;
        the_iterator++;
      }
      cout << "Total=" << total << endl;
Notice that you can access the elements of the container by dereferencing the iterator.