A pushdown stack is an ADT that comprises two basic operations: insert (push) a new item, and remove **(pop) **the item that was most recently inserted.
items are removed according to a last-in, first-out (LIFO) discipline.
Each push increases the size of the stack by 1 and each pop decreases the size of the stack by 1.
Pushdown-stack ADT interface
template <class Item>
class STACK
{
private:
// Implementation-dependent code
public:
STACK(int);
int empty() const;
void push(Item item);
Item pop();
};
First line in above interface gives a C++ template to the class.
STACK<int> save(N)
This declaration specifies that the type of items on stack named save is to be int (and max number of item in the stack might need to hold at any one time is N).