How do I pick apart the characters of an input?

Question

Please describe how it works!

Answer 1

a full description will be too much to type in here.

start looking up lexing, maximal munch, tokenization. you will be headed in the right direction.

edit: for a good reference, look into ruslan spivak's posts on building an interpreter or www.craftinginterpreters.com. both are excellent to learn from and they intend to teach.