What qualifies as a digit depends on the radix
(an integer between 2 and 36, inclusive).
The potential digits are:
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 R S T U V W X Y Z
Their respective weights are 0, 1, 2, ... 35.
In any given radix n, only the first n potential digits
are considered to be digits.
For example,
the digits in radix 2 are 0 and 1,
the digits in radix 10 are 0 through 9, and
the digits in radix 16 are 0 through F.
Case is not significant in digits;
for example, in radix 16, both F and f
are digits with weight 15.