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

int main() {
    int  a = 10;
    int *p = &a;
    printf("%d\n", a);
    printf("%p\n", &a);
    printf("%d\n", *p);
    *p = 30;
    printf("%d\n", a);
    
    printf("-----------------------------------------------\n");
    
    int arr[3] = {10, 20, 30};
    int *p1 = arr;
    printf("%d\n", *p1);
    printf("%d\n", *(p1+1));
    printf("%d\n", *(p1+2));
    
    printf("-----------------------------------------------\n");

    int *p2 = malloc(sizeof(int)*4);
    if (p2==NULL) return 1;
    p2[0] = 10;
    p2[1] = 20;
    free(p2);
    p2 = NULL;
}