I know how to present number as a bitmap, for instance:
17 = 010001
11 = 001011
This is about numbers, but what about letters? Is there a way to do this? For example:
w = ??
[ = ??
Everything on your computer is represented as a sequence a bits, what you are calling a “bitmap”. So the answer to your question is yes, characters have a binary representation, along with integers, floating-point numbers, machine instructions etc.
Different languages use different binary encodings for characters, Objective-C uses Unicode. See the section Understanding Characters in the NSString
documentation.
HTH