Data Structures using C++

  #include< iostream.h> 
  #include< conio.h> 
  #define SIZE 20 
  class stack 
  { 
    int a[SIZE]; 
    int tos; // Top of Stack 
    public: 
       stack(); 
       void push(int); 
       int pop(); 
       int isempty(); 
       int isfull(); 
  }; 
  stack::stack() 
  { 
    tos=0; //Initialize Top of Stack 
  } 
  int stack::isempty() 
  { 
    return (tos==0?1:0); 
  } 
  int stack::isfull() 
  { 
    return (tos==SIZE?1:0); 
  } 
  void stack::push(int i) 
  { 
    if(!isfull()) 
    { 
      cout<<"Pushing "<< i<< endl; 
      a[tos]=i; 
      tos++; 
    } 
    else 
    { 
      cerr<<"Stack overflow error ! 
      Possible Data Loss !"; 
    } 
  } 
  int stack::pop() 
  { 
    if(!isempty()) 
    { 
      cout<<"Popping "<< a[tos-1]<< endl; 
      return(a[--tos]); 
    } 
    else 
    { 
      cerr<<"Stack is empty! What to pop...!"; 
    } 
    return 0; 
  } 
  void reverse(stack s) 
  { 
    stack s2; 
    while(!s.isempty()) 
    { 
       s2.push(s.pop()); 
    } 
    cout<<"Reversed contents of the stack..."<< endl; 
    while(!s2.isempty()) 
    { 
       cout<< s2.pop()<< endl; 
    } 
  }//end of fn. 
  void main() 
  { 
    clrscr(); 
    stack s; 
    s.push(1); 
    s.push(2); 
    s.push(3); 
    reverse(s); 
    getch(); 
  }