base 16 is a positional numeral system with sixteen as its base. It uses 16 different digits for representing numbers. The digits for base 16 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, and f.

base 28 is a positional numeral system with twenty-eight as its base. It uses 28 different digits for representing numbers. The digits for base 28 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, and r.