Enqueue means to insert an item into the back of the queue, dequeue means inserting the front item.

An iteration is a data structure, which can store a fixed size collection of elements of the same data type.

A queue is a collection of entities that are maintained in a sequence and can be modified by the addition of entities at one end of the sequence and removal from the other end of the sequence.

The acronym LIFO stands for Long in First Out.

An invariant is a statement about program variables that is true every time the execution of the program reaches the invariant.

A recursive function calls itself, the memory for a called function is allocated on top of a memory allocated to calling function and different copy of local variables is created for each function call.

In an entry controlled loop, a condition is checked before executing the body of a loop, it is called pre-checking loop.

Indexed array are arrays that with name keys.