Most large applications have one thing in common: they are built to work with a database. All the calculation in the world means nothing without data to perform it on. Think of the rules of any sport. The rules are there to make sure decorum is upheld, and to determine who the winner is. Rules mean very little without the teams who make the score.
Similarly, business processes and calculations mean very little unless they involve real-world data. But in order to get at that data, or to store it, or to change it, we need code to connect to a database and perform the various functions required. That is the code we seek to create ...