implementing a dynamically sized stack using an array.

//Consider implementing a dynamically sized stack using an array.
#include<stdio.h>
#include<stdlib.h>
struct stack
{
int *a;
int top;
int maxSize;
};
void initstack(struct stack *p,int maxSize){
    p->top = -1;
    p->a = (int*)malloc(maxSize*sizeof(int));
    p->maxSize = maxSize;
}
void push(struct stack * p, int item){
    if((p->top) == (p->maxSize)-1){
        printf("Stack is full\n");
    }
    else{
        p->top++;
        p->a[p->top]=item;
    }
}
int pop(struct stack *p){
    if(p->top == -1){
        printf("Stack is empty\n");
        return -1000;
    }
    else{
        int t = p->a[p->top];
        p->top--;
        return t;
    }
}
void display(struct stack p){
    int i;
    if(p.top==-1){
        printf(" {}\n");
    }
    else{
    for(i=0;i<p.top;i++){
        printf(" %d",p.a[i]);
    }
    printf(" %d",p.a[i]);
    printf("\n");
}}
int main(){
    struct stack s;
    int n,choice,t;
    printf("Enter the maximum size of the stack\n");
    scanf("%d",&n);
    initstack(&s,n);
    do{
    printf("Choice 1 : Push\nChoice 2 : Pop\nChoice 3 : Display\nAny other choice : Exit\nEnter your choice\n");
    scanf("%d",&choice);
    switch(choice){
        case 1:{
            printf("Enter the element to be pushed\n");
            scanf("%d",&t);
            push(&s,t);
            break;
        }
        case 2:{
            int nn = pop(&s);
            if(nn!=(-1000)){
                printf("The popped element is %d\n",nn);
            }
            break;
        }
        case 3:{
            printf("The contents of the stack are");
            display(s);
            //printf("\n");
            break;
        }
    }
    }while(choice<=3 && choice!=0);
    return 0;
}