stack DS

/* Implementation of stack in C */

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

#define SIZE 3

struct stak{

    int stack[SIZE];
    int top;
}stackvar;

int isFull();
int isEmpty();
void push(int);
int pop();
void peek();
void display();

int main()
{
    stackvar.top = -1;
    int option, element;
    while(1)
    {
        printf("\n\nENTER YOUR OPTION\n");
        printf("1. PUSH\n2. POP\n3. PEEK\n4. DISPLAY\n5. EXIT\n");
        scanf("%d",&option);
        switch(option)
        {
            case 5: exit(0);
            case 1: printf("ENTER ELEMENT TO PUSH\n");
                    scanf("%d",&element);
                    push(element);
            break;
            case 2:printf("%d HAS BEEN POPPED\n",pop());
            break;
            case 3:peek();
            break;
            case 4:display();
            break;
            default: printf("INVALID OPTION\n");
        }
    }
    return 0;
}

int isFull()
{
    return stackvar.top == SIZE-1;
}
int isEmpty()
{
    return stackvar.top == -1;
}
void push(int ele)
{
    if(isFull())
    {
        printf("STACK IS FULL, CANT PUSH\n");
    }
    else
    {
        stackvar.stack[++stackvar.top] = ele;
        printf("%d HAS BEEN PUSHED\n",ele);
    }

}
int pop()
{
    if(isEmpty())
    {
        printf("THE STACK IS EMPTY, CAN'T POP\n");
        return -1;
    }
    return stackvar.stack[stackvar.top--];
}
void peek()
{
    if(!isEmpty())
        printf("\nTOP OF THE STACK IS %d\n",stackvar.stack[stackvar.top]);
    else
        printf("STACK IS EMPTY\n");
}

void display()
{
    int i;
    i = stackvar.top;
    if(!isEmpty())
        while(i != -1)
            printf("\n\t%d\n",stackvar.stack[i--]);
    else
        printf("STACK IS EMPTY\n");
}