systems

Given that this is not mentioned in either our notes or our lectures (and I will explain why later), I don’t know why you are asking me to explain. Wherever you read about it must surely explain, or alternatively you could have used Google to find out what it is!!

It is not mentioned in our notes because it is not mentioned in the syllabus and is now rather irrelevant given the existence of the internet.

Before the internet, people used to access databases by using a telephone link to their computer, connecting to the database, and then entering a password. There was always the risk that someone else had ‘stolen’ the password and was dialling in. What happened with dial-back was that you would ring, and enter the password, but instead of then being connected to the database, the other computer would ring off. Given than because of the password it would know who you were, the computer would ring your computer back on your number. So it it was a ‘thief’ ringing from a different number, they would not get access.

Please stop asking me about things you find in other books. My notes and lectures cover everything needed to pass the exam well – ask about things you are not clear about from my notes and lectures, or from questions in your Revision Kit (assuming it is a current edition).