This example code is explained in the STXXL Queue section.
#include <iostream>
int main()
{
queue my_queue;
my_queue.push(11);
my_queue.push(3);
my_queue.push(7);
assert(my_queue.size() == 4);
std::cout << "back element " << my_queue.back() << std::endl;
assert(my_queue.back() == 7);
std::cout << "front element " << my_queue.front() << std::endl;
assert(my_queue.front() == 5);
my_queue.pop();
std::cout << "front element " << my_queue.front() << std::endl;
assert(my_queue.front() == 11);
return 0;
}