Can't get string from Serial Monitor! Please Help!

Thanks a lot wvmarle!
I thought that the decimal value of an hex representation is concatenation of each
hex digit's decimal value, in my case, D=13, E=14,so the result is 1314 !
The fact that are so many topics about "storing MAC address" is because,like me, newbies fail to
know/understand hex representation !
Please,if you don't mind, can you tell me how does that work?

P.S: I haven't used yet the code above, cause first I want to know exactly how hex representation
works.Thank you!