A quaint system of counting that only uses just the first A digits, with numbers going straight from 9 to 10.

Each digit represents a power of A, rather than a power of 10 so, for example, 234 represents 2*A*A + 3*A + 4 = C8 + 1E + 4 = EA. Similarly, 42 represents the number 2A.

With practice, calculation can be done without converting back to hex first.