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

#define  SIZE  100

typedef struct tray {
   char  color[ 10 ];    /* its color */
   int   id;             /* its unique id number */
} TRAY;

TRAY *trays[ SIZE ]; /* array to hold up to SIZE pointers to TRAY */
int   top = -1;      /* index into trays */

void  get_data( TRAY *ptr ), put_data( const TRAY *ptr );
TRAY *pop( void ), *push( TRAY tr );

main()
{
     int   ans, flag;
     TRAY t, *ptr;

     /* do stack operations until user signals halt */
     do {
          do {
               printf( "\n\n\tEnter 1 to push, 2 to pop:  " );
               scanf( "%d", &ans );
               printf( "\n" );
               switch ( ans ) {
               case 1: /* get a TRAY and add it to stack */
                    get_data( &t );
                    if ( push( t ) == NULL )
                         printf( "\n\nSTACK FULL\n\n" );
                    break;
               case 2: /* delete a TRAY from stack and print it */
                    if ( ( ptr = pop() ) != NULL )
                         put_data( ptr );
                    else
                         printf( "\n\nSTACK EMPTY\n\n" );
                    break;
               default:
                    printf( "\nIllegal response\n" );
                    break;
               }
          } while ( ans != 1 && ans != 2 );
          printf( "\n\n\n1 to continue, 0 to quit: " );
          scanf( "%d", &flag );
          printf( "\n" );
     } while ( flag );

     return EXIT_SUCCESS;
}

/*   get_data prompts the user for a TRAY's color and id and stores
     it at the address passed.                                     */

void  get_data( TRAY *ptr )
{
     printf( "\nenter the tray's color: " );
     scanf( "%s", ptr -> color );
     printf( "\nenter the tray's id: " );
     scanf( "%d", &( ptr -> id ) );
     printf( "\n" );
}

/*   put_data writes the color and id of the TRAY whose address is
     passed.                                                       */

void put_data( const TRAY *ptr )
{
     printf( "\ntray's color: %s\n", ptr -> color );
     printf( "\ntray's id: %d\n", ptr -> id );
}

/*   If the stack is full, push returns NULL. Otherwise, push
     allocates storage for a TRAY, copies the data passed into the
     allocated storage, pushes a pointer to the TRAY onto the stack,
     and returns the address of the TRAY added. */
TRAY  *push( TRAY tr )
{
     TRAY *ptr;

     if ( top  >=  SIZE - 1 ) /* stack full? */
          return NULL;
     ptr = malloc( sizeof ( TRAY ) ); /* new TRAY */
     *ptr = tr; /* store data */
     trays[ ++top ] = ptr;  /* push it and update top */
     return ptr;
}

/*   If the stack is empty, pop returns NULL. Otherwise, pop copies
     the top TRAY to permanent storage, frees the stack storage,
     updates top, and returns the address of the TRAY.            */

TRAY *pop( void )
{
     static TRAY popped_tray;

     if ( top < 0 ) /* empty stack? */
          return NULL;

     popped_tray = *trays[ top ]; /* copy top TRAY */
     free( trays[ top-- ] ); /* collect garbage */
     return &popped_tray;
}