Implement stack and perform push, and pop operations

/* Write a C program to implement stack. Stack is a LIFO data strcuture    *
 * LIFO - Last in First Out                                                *
 * Perform PUSH(insert operation), POP(Delete operation) and Display stack */

#include <stdio.h>
#include <conio.h>
#define MAXSIZE 5


struct stack            /* Structure definition for stack */
{
 int stk[MAXSIZE];
 int top;
};

typedef struct stack STACK;
STACK s;

/* Function declaration/Prototype*/

void push (void);
int  pop(void);
void display (void);

void main ()
{
 int choice;
 int option = 1;

 clrscr ();

 s.top = -1;

 printf ("STACK OPERATION\n");
 while (option)
 {
  printf ("------------------------------------------\n");
  printf ("   1 --> PUSH            \n");
  printf ("   2 --> POP            \n");
  printf ("   3 --> DISPLAY            \n");
  printf ("   4 --> EXIT     \n");
  printf ("------------------------------------------\n");

  printf ("Enter your choice\n");
  scanf ("%d", &choice);
  
  switch (choice)
  {
   case 1: push();
    break;
   case 2: pop();
    break;
   case 3: display();
    break;
   case 4: return;
  }

  fflush (stdin);
  printf ("Do you want to continue(Type 0 or 1)?\n");
  scanf ("%d", &option);
 }
}

/*Function to add an element to the stack*/
void push ()
{
 int num;
 if (s.top == (MAXSIZE - 1))
 {
  printf ("Stack is Full\n");
  return;
 }
 else
 {
  printf ("Enter the element to be pushed\n");
  scanf ("%d", &num);
  s.top = s.top + 1;
  s.stk[s.top] = num;
 }
 return;
}


/*Function to delete an element from the stack*/
int pop ()
{
 int num;
 if (s.top == - 1)
 {
  printf ("Stack is Empty\n");
  return (s.top);
 }
 else
 {
  num = s.stk[s.top];
  printf ("poped element is = %d\n", s.stk[s.top]);
  s.top = s.top - 1;
 }
 return(num);
}

/*Function to display the status of the stack*/
void display ()
{
 int i;
 if (s.top == -1)
 {
  printf ("Stack is empty\n");
  return;
 }
 else
 {
  printf ("\nThe status of the stack is\n");
  for (i = s.top; i >= 0; i--)
  {
   printf ("%d\n", s.stk[i]);
  }
 }
 printf ("\n");
}

/*---------------------------------------------------------------------------
Output
STACK OPERATION
------------------------------------------
 1       -->     PUSH
        2       -->     POP
 3       -->     DISPLAY
        4       -->     EXIT
------------------------------------------
Enter your choice
1
Enter the element to be pushed
23
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
 1       -->     PUSH
        2       -->     POP
 3       -->     DISPLAY
        4       -->     EXIT
------------------------------------------
Enter your choice
1
Enter the element to be pushed
45
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
    1       -->     PUSH
        2       -->     POP
    3       -->     DISPLAY
        4       -->     EXIT
------------------------------------------
Enter your choice
1
Enter the element to be pushed
78
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
        1       -->     PUSH
        2       -->     POP
 3       -->     DISPLAY
        4       -->     EXIT
------------------------------------------
Enter your choice
3

The status of the stack is
78
45
23

Do you want to continue(Type 0 or 1)?
1
------------------------------------------
        1       -->     PUSH
 2       -->     POP
        3       -->     DISPLAY
        4       -->     EXIT
------------------------------------------
Enter your choice
2
poped element is = 78
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
        1       -->     PUSH
 2       -->     POP
        3       -->     DISPLAY
        4       -->     EXIT
------------------------------------------
Enter your choice
3

The status of the stack is
45
23

Do you want to continue(Type 0 or 1)?
0
-----------------------------------------------------------------------------*/