b) real-time processing :

real-time is a term used to describe a process or event that occurs immediately.
For example, chat program occur in real-time, where messages are seen immediately after the user presses his or her enter key

real-time operating system :

For example:
In a bank transaction, Bob tried to deposit money to his account.

In REAL TIME, the money is DEPOSITED right away as soon as Bob handed the money.. and there's no turning back! :)