stack using array

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

struct stack{
    int size;
    int top;
    int *arr;
};

int isEmpty(struct stack *ptr){
    if(ptr->top==-1){
        return 1;
    }
    return 0;
}

int isFull(struct stack*ptr){
    if(ptr->top == ptr->size-1){
        return 1;
    }
    return 0;
}


int main() {
    // struct stack s;
    // s.size=80;
    // s.top=-1;
    // s.arr = (int*)malloc(s.size*sizeof(int));
    
    struct stack *s; 
    s->size=80;
    s->top=-1;
    s->arr = (int*)malloc(s->size*sizeof(int));
    
    s->arr[0]=7;
    s->top++;
    
    if(isEmpty(s)){
        printf("stack is empty");
    }
    else{
        printf("stack is full");
    }
    
    return 0;
}