What Is a System Interface?
Imagine you want to charge your phone, but your charger and smartphone have different connectors. Or you get into a new car and can’t immediately figure out how to turn on the headlights. Why does this happen? It all comes down to the interface!
When we interact with any system, we don’t see its internal structure—it’s a black box to us. But for the system to function, it needs clear points of interaction. These points are defined by interfaces. When describing a system as a black box, we’re only interested in how the system interacts with the outside world, without delving into its internal workings.
An interface is a description of the rules and standards for how a system interacts with the external world. It exists as a mental or informational concept and does not have a physical form. However, for interaction to actually occur, an interface module is needed—a physical object that implements the interface. The interface defines how the interaction should happen, while the interface module ensures the physical execution of these rules.
The interface is part of the system’s description, but it is not the system itself. It defines how data can be input into the system, how to obtain the results of its operation, and what constraints exist on inputs and outputs.
Example: A car as a system. In this system, the interface is the set of rules for how the driver interacts with the car. It specifies what actions the driver must take to send commands to the vehicle. For instance, the car’s control interface includes rules such as: “turning the steering device changes the direction of movement,” “pressing the acceleration device increases speed,” and “activating the start device starts the engine.” In turn, the interface module is the physical object that implements the described interface. In a car, these modules are the steering wheel (steering device), gas pedal (acceleration device), and engine start button. Here, the black box concept explains that the driver does not see how the car functions or how the engine converts fuel into motion, but interacts with the system through interface modules—that is, controls the car.
In this example, we can identify the following interfaces and their interface modules:
– physical interface: the rules for interacting with mechanical control elements; interface modules include pedals, steering wheel, and dashboard buttons;
– informational interface: the rules for providing the driver with information about the car’s status; interface modules include the speedometer, fuel indicators, and dashboard display;
– energy interface: the rules for supplying energy to the car; interface modules include the fuel tank and the charging port of an electric vehicle;
– voice interface: the rules for voice interaction with the car; interface modules include the microphone, voice processor, and audio system.
If every car had a unique control interface, drivers would have to retrain before every trip. It is the standardization of interfaces that makes driving understandable and universal.
To sum up: An interface is an immaterial concept that describes the rules for how a system interacts with the external world. An interface module is the physical component that implements the interface. The interface is part of the system’s black box description, but it is not the system itself. Without interfaces, systems cannot interact with each other or with users. We live in a world of interfaces—from cars and gadgets to language and social interactions. And the better the interface is designed, the easier and more convenient it is to work with the system!