typedef struct _node *Quack;

Quack createQuack(void);     // create and return Quack
void  push(int, Quack);      // put the given integer onto the quack
void  qush(int, Quack);      // put the given integer onto the quack
int   pop(Quack);            // pop and return the top element on the quack
int   isEmptyQuack(Quack);   // return 1 if Quack is empty, else 0
void  makeEmptyQuack(Quack); // remove all the elements on Quack
void  showQuack(Quack);      // print contents of Quack, from the top down