#include <stdio.h>
#include <stdlib.h>

/* self-referential structure */
struct stackNode
 {
  int data; /* define data as an int */
  struct stackNode *nextPtr; /* stackNode pointer */
 }; /* end structure stackNode */

typedef struct stackNode StackNode; /* synonym for struct stackNode */
typedef StackNode *StackNodePtr; /* synonym for StackNode* */

/* prototypes */
void push( StackNodePtr *topPtr, int info );
int pop( StackNodePtr *topPtr );
void instructions( void );
void printStack( StackNodePtr currentPtr );
int isEmpty( StackNodePtr topPtr );

/* function main begins program execution */
int main()
{
  StackNodePtr stackPtr = NULL; /* points to stack top */
  int choice; /* user's menu choice */
  int value; /* int input by user */

  instructions(); /* display the menu */
  printf( "? " );
  scanf( "%d", &choice );

  /* while user does not enter 3 */
  while ( choice != 3 ) {

    switch ( choice ) {

      /* push value onto stack */
    case 1:
      printf( "Enter an integer: " );
      scanf( "%d", &value );
      push( &stackPtr, value );
 printStack( stackPtr );
      break;

      /* pop value off stack */
    case 2:

      /* if stack is not empty */
      if ( !isEmpty( stackPtr ) ) {
        printf( "The popped value is %d.\n", pop( &stackPtr ) );
      } /* end if */

      printStack( stackPtr );
      break;

    default:
      printf( "Invalid choice.\n\n" );
      instructions();
      break;

    } /* end switch */
  printf( "? " );
    scanf( "%d", &choice );
  } /* end while */

  printf( "End of run.\n" );

  return 0; /* indicates successful termination */

} /* end main */

/* display program instructions to user */
void instructions( void )
{
  printf( "Enter choice:\n"
"1 to push a value on the stack\n"
"2 to pop a value off the stack\n"
          "3 to end program\n" );
} /* end function instructions */

/* Insert a node at the stack top */
void push( StackNodePtr *topPtr, int info )
{
  StackNodePtr newPtr; /* pointer to new node */

  newPtr = malloc( sizeof( StackNode ) );

  /* insert the node at stack top */
  if ( newPtr != NULL ) {
    newPtr->data = info;
    newPtr->nextPtr = *topPtr;
    *topPtr = newPtr;
  } /* end if */
  else { /* no space available */
    printf( "%d not inserted. No memory available.\n", info );
  } /* end else */

} /* end function push */

/* Remove a node from the stack top */
int pop( StackNodePtr *topPtr )
{
  StackNodePtr tempPtr; /* temporary node pointer */
 int popValue; /* node value */

  tempPtr = *topPtr;
  popValue = ( *topPtr )->data;
  *topPtr = ( *topPtr )->nextPtr;
  free( tempPtr );

  return popValue;

} /* end function pop */

/* Print the stack */
void printStack( StackNodePtr currentPtr )
{
  
I'm stuck here!
 } /* end function printList */

/* Return 1 if the stack is empty, 0 otherwise */
int isEmpty( StackNodePtr topPtr )
{

And here.

} /* end function isEmpty */

void printStack(StackNodePtr cur)
{
     int x;
     if (cur) {
         x = pop(&cur);   // Pop it off the stack. 
         printf("%d\n", x);  // Print it. 
         printStack(cur);  // Now print the REST of teh stack. 
         push(x);           // Stick it back on again. 
     }
}