cppreference.com > C++ Stacks empty Syntax:
      #include <stack>
      bool empty() const;
The empty() function returns true if the stack has no elements, false otherwise. For example, the following code uses empty() as the stopping condition on a (C/C++ Keywords) while loop to clear a stack and display its contents in reverse order:
     vector<int> v;
     for( int i = 0; i < 5; i++ ) {
       v.push_back(i);
     }
     while( !v.empty() ) {
       cout << v.back() << endl;
       v.pop_back();
     }
Related topics: size

pop
Syntax:

      #include <stack>
      void pop();

The function pop() removes the top element of the stack and discards it.

Related topics:
(C++ Priority Queues) push
top

push
Syntax:

      #include <stack>
      void push( const TYPE& val );

The function push() adds val to the top of the current stack.

For example, the following code uses the push() function to add ten integers to the top of a stack:

       stack<int> s;
       for( int i=0; i < 10; i++ )
         s.push(i);

Related topics:
pop

size
Syntax:

      #include <stack>
      size_type size() const;

The size() function returns the number of elements in the current stack.

Related topics:
(C++ Strings) capacity
empty
(C++ Strings) length
(C++ Multimaps) max_size
(C++ Strings) resize

top
Syntax:

      #include <stack>
      TYPE& top();

The function top() returns a reference to the top element of the stack.

For example, the following code removes all of the elements from a stack and uses top() to display them:

       while( !s.empty() ) {
         cout << s.top() << " ";
         s.pop();
       }

Related topics:
pop

Stack constructors
Syntax:

      #include <stack>
      stack();
      stack( const Container& con );

Stacks have an empty constructor and a constructor that can be used to specify a container type.