How to study

hie everyone . my cs attempt is in this dec. as I am preparing self I have many doubts. my query is I am studying the institute books and I have not bought any author book except for tax. in institute books after completion of each chapter there are very few self test questions. I want to know for practice I have to buy scanners for all subjects or not . plzz replyy. and tell me the name of those scanners. plzz help..