How was the reference counting mechanism implemented in ARC's automatic memory management?

In ARC (Automatic Reference Counting), the reference counting mechanism is implemented at the compiler and runtime level. Each object contains a reference count — the number of active references to it. When a new reference is created, the count increases; when a reference is removed, it decreases. When the count reaches zero, the object is automatically deallocated. This allows memory management without explicit deallocation calls, reducing leaks and errors.