Program to implement Stack in C

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

#include <stdio.h>
#include <conio.h>
#define MAX SIZE 5


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


typedef struct stack STACK;
STACK s;


/* Function declaration*/


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 ("wish 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 element from  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


----------------------------------------------------------------*/