The following are the cases when you don't get CS in BITS:- (i)JEE AIR-1,Achin Bansal feels he is not good enough to get into IIT and decides to go for BITS instead. (ii)The computer prog. at BITS fallters and starts awarding seat to ranks in decreasing order......50000..49999..49998..49997..and so on. (iii)BITS introduce a formula of : "FIRST COME FIRST SERVE"
Except these unavoidable , unlucky situations you would certainly get CS in BITS