hey guys i’m fairly new to the subject and haven’t start trading yet but had a doubt on short selling.
It is said that if the seller doesn’t buy back the shares, he gets defaulted in short selling.
But as to the extent of my knowledge doesnt the exchange itself squares off his position in intra day?
please explain. 
@ganya : If sold intraday you must either buy eod or give delivery of shares. there is no provision at exchange level to square off the trade as it is not possible to know your intent , if you want to deliver or square off. however some brokers ( not all )make some client specific ( not for all ) rules to auto square such trade if pending beyond a time say 3.20 pm .
Shares of XT , T ,Z , P group can not be squared off also but must compulsorily result in delivery.
Okay and in short selling the shares of that are are being short sold should be from my portfolio right?