How do I print bytes as hexadecimal?

If you want to use C++ streams rather than C functions, you can do the following:

int ar[] = { 20, 30, 40, 50, 60, 70, 80, 90 };
const int siz_ar = sizeof(ar) / sizeof(int);

for (int i = 0; i < siz_ar; ++i)
    cout << ar[i] << " ";
cout << endl;

for (int i = 0; i < siz_ar; ++i)
    cout << hex << setfill('0') << setw(2) << ar[i] << " ";
cout << endl;

Very simple.

Output:

20 30 40 50 60 70 80 90
14 1e 28 32 3c 46 50 5a