stack

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
 
#define MAX 50
int size;
 
// Defining the stack structure
struct stack {
   int arr[MAX];
   int top;
};
 
// Initializing the stack(i.e., top=-1)
void init_stk(struct stack *st) {
   st->top = -1;
}
 
// Entering the elements into stack
void push(struct stack *st, int num) {
   if (st->top == size - 1) {
      printf("\nStack overflow(i.e., stack full).");
      return;
   }
   st->top++;
   st->arr[st->top] = num;
}
 
//Deleting an element from the stack.
int pop(struct stack *st) {
   int num;
   if (st->top == -1) {
      printf("\nStack underflow(i.e., stack empty).");
      return (0);
   }
   num = st->arr[st->top];
   st->top--;
   return num;
}
 
void display(struct stack *st) {
   int i;
   for (i = st->top; i >= 0; i--)
      printf("\n%d", st->arr[i]);
}
 
int main() {
   int element, opt, val;
   struct stack ptr;
   init_stk(&ptr);
   printf("\nEnter Stack Size :");
   scanf("%d", &size);
   while (1) {
      printf("\n\ntSTACK PRIMITIVE OPERATIONS");
      printf("\n1.PUSH");
      printf("\n2.POP");
      printf("\n3.DISPLAY");
      printf("\n4.QUIT");
      printf("\n");
      printf("\nEnter your option : ");
      scanf("%d", &opt);
      switch (opt) {
      case 1:
         printf("\nEnter the element into stack:");
         scanf("%d", &val);
         push(&ptr, val);
         break;
      case 2:
         element = pop(&ptr);
         printf("\nThe element popped from stack is : %d", element);
         break;
      case 3:
         printf("\nThe current stack elements are:");
         display(&ptr);
         break;
      case 4:
         exit(0);
      default:
         printf("\nEnter correct option!Try again.");
      }
   }
   return (0);
}