QUestion on C language

Respected sir, I am Bhuvan Gupta, a B.Tech student.(got your id from yours " USB LED driver - 1.1 ") ) With due respect, I humbly request you to please throw some light on to below written question. i will highly appreciate your efforts. [1] when we use C language,we use diferent library to do different thing.As also in your case you use module.h,init.h etc but how to write this library , in what language they are written in as standard ANSI C has round about 32 keywords ? what should i read and learn to the related topic . please suggest something (I do have knowledge of Assembly). please help,this question making me beacen it will be honour if you reply. thank you Bhuvan Gupta India