hello , I would like to develop APP of bitcoin exchanges , but I cannot get any source of it,  even at GitHub, most of it just have introduced  API his own app. .. and even I can't get basic source of it.   anybody help to let me know any website or source of it?

ps. I means, I want to know how to exchages bitcoin address works , does bitcoin address of exchages have many address that be given for users, ?

and is it called hot wallet? ,   thanks.