when the symbols first didget are exhausted, the next-higher didget(to the left) is incremented, and counting starts over at 0. in decimal, counting proceeds on like so:
00, 01, 02, ... 07, 08, 09(rightmost didgit starts over, and the 0 is incremented)
10, 11, 12, ... 17, 18, 19( again)
20, 21, 22, ...
when the rightmost didgit reaches 9, counting returns to 0, and the second didgit is incremented. In binary, counting is similar, with the exception that only the symbols 0 and 1 are used. When 1 is reached, counting begins at 0 again, with the didgit to the left being incremented:
000, 001 (rightmost didgit starts over)
010, 011 (both middle and rightmost)
100, 101 (rightmost)
110, 111...
