Object‐Oriented Programming (OOP) Practice Test

Fan-in describes how many external components rely on a given module; it counts incoming dependencies from outside to inside. This matches the idea that many other parts of the system depend on this module, so its change impact spans those dependents. If a module is used by many others, it has high fan-in, which can make changes riskier because breaking it could affect many callers. In contrast, fan-out refers to how many external components a module itself depends on (outgoing dependencies), not how many depend on it. The total number of interfaces measures how many entry points the module exposes, and the number of public methods reflects API size, not dependency direction. For example, if a module is used by three other modules, its fan-in is three; if it calls two other modules, that’s its fan-out.