The char datatype can be treated as its unicode equivalent without typecasting or converting. So it's is evaluating the chars based on their unicode equivalents. If you're not familiar with Unicode you definetly need to research it.

Just need to store digits 1-9, 10-90 (in multiples of 10), and store hundred thousand million

how does the input even work?

I love this!!!

If it fails due to it taking too long you need to think of the problem differently. It took me a bit however it is much more simple than you think.

I never knew char's worked like this, learn something new everyday.

Wait im confused, this probably a dumb question but where do you access the alphabet in this?

This is what happens when you don't know all the neat tricks that come with c#. If only i knew that String constructors existed.