A stack is a last in, first out (LIFO) abstract data type and sequential data structure. A stack may have any abstract data type as a component, but is characterized by two fundamental functions, called pop and push. The push operation includes a new item to the top of the stack, or starts the stack if it is empty. If the stack is full and does not have enough space to locate the given item, the stack is then goes to be in an overflow state. The pop operation replaces an item from the top of the stack. A pop either converts previously concealed results, or items in an empty stack, but if the stack is empty then it bond into underflow state. A stack pointer is the register which acquires the value of the stack. The stack pointer usually points to the top value of the stack.

A stack is a limited data structure, because only small values of operations are performed on it. The nature of the push and pop operations also seems that stack elements have a sequential order. Components are removed from the stack in the reverse order to the specific order of their addition: therefore, the lower components are those that have been on the stack the longest.