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Functions are an elementary part of programming languages. With them, programs can be simplified and presented in a manageable and reusable way (modularisation). Functions also help us to keep our code organised and understandable. 

Functions act as jumps in the program. In the event of a function call, the program jumps to the position where the function is defined and then returns after the function has been executed. Most programming languages have many built-in or native functions. To find out how the Processing functions work, and what parameters they expect, we need to look at the processing documentation (https://processing.org/reference/).

In the previous examples, we have written programs without functions. These programs were not interactive and do not include animations. So how can you extend a program so that, for example, the keyboard is used as an input? The answer is to use program events, which are recorded and forwarded by the program. Here is a short list of some such events:

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Exercise 3:

Take your results to form exercise 2, and modify it so it animates across the screen. 

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