What kind of technology is used in banking?

What kind of technology is used in banking?
There are two systems generally used the Online real time system and the offline system.The offline system works whenever we deposit money at a bank.Hence our balance increases only at the end of the working day and not before.It is cheaper than the online version.The online version is used for making withdrawals where in the update of a withdrawal is directly sent to the main server as the transaction is processed and your account balance lessens at that point. Otherwise you could overdraw your a/c by 100 times and the bank would only be notified the next day !!!