The system is the computer program that interacts with the human user. The system needs to be able to interpret the actions of the human user, perform calculations, modify any data it might be working with, and modify its behaviour according to what the user needs and wants. It’s also worth noting that the system is very rarely a stand-alone entity. It’s usually sitting on top of a whole host of digital infrastructure that creates several layers of abstraction between the human user and the system itself. For example, if you click the mouse on your computer, it’s the operating system (for instance, Windows or maybe Mac) that first “realizes” that the mouse has been clicked. It’s the operating system that passes along this information to other programs that are running on the computer.