STACKS- Using Structures

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

/* Defines the stack size */
#define STACK_SIZE 5

/* Structure defining stack */
struct stack
{
	int data[STACK_SIZE];
	int top;
};
/* Creating the data type STACK */
typedef struct stack STACK;

/* Function Declarations */
int isFull(STACK);
int isEmpty(STACK);
void push(STACK*);
void pop(STACK*);
void display(STACK);

void main()
{
	STACK s;
	int choice;

	/* Stack top initial condition / empty condition is always set to -1 */
	s.top = -1;

	printf("\nProgram to implement stacks\n");

	for(;;)
	{
		printf("\n1. Push\n2. Pop\n3. Display\n4. Exit\n");
		printf("Please enter the choice\t");

		scanf("%d", &choice);

		switch(choice)
		{
			case 1:	push(&s);
				break;
			case 2:	pop(&s);
				break;
			case 3:	display(s);
				break;
			case 4: exit(0);
			default:	printf("Invalid selection\nPlease re-enter\n");
		}
	}
}

int isFull(STACK s)
{
	return (s.top == STACK_SIZE -1) ? 1 : 0;
}

int isEmpty(STACK s)
{
	return (s.top == -1) ? 1 : 0;
}

void push(STACK *s)
{
	int item;

	printf("Please enter the item to be inserted\n");
	scanf("%d", &item);

	if(isFull(*s))
	{
		printf("Cannot push %d into the stack\nStack overflow!!!\n", item);
		return;
	}

	/* Increment top and set the top to appropriate position */
	s->top++;
	printf("Item %d will be inserted at %d position\n", item, s->top + 1);
	/* Insert the item given by the user onto the top of stack */
	s->data[s->top] = item;
}

void pop(STACK *s)
{
	if(isEmpty(*s))
	{
		printf("Cannot pop from stack\nStack underflow!!!\n");
		return;
	}

	printf("%d is the element popped out of stack\n",s->data[s->top]);
	/* Decrement the top to delete the element of stack */
	s->top--;
}

void display(STACK s)
{
	int i;

	if(isEmpty(s))
	{
		printf("Cannot print contents of stack\nStack underflow!!!\n");
		return;
	}

	printf("Printing contents of stack\n");

	for(i = 0; i <= s.top; i++)
	{
		printf("%d\n",s.data[i]);
		sleep(1);
	}
}