#include <stdio.h>
#include <stdint.h>

int main(int argc, char const *argv[])
{
    uint8_t a[256] = {};
    uint8_t *ptr;
    size_t n = 128;

    ptr = a;
    a[n] = 16;

    for (int i = 0; i < sizeof(a)/sizeof(a[0]); ++i) {
        if ( i == n )
            printf("a[%lu] = %u", n, *ptr);
        ptr++;
    }

    return 0;
}