Where in the application is the Singleton component instance usually implemented and stored?

An instance of a Singleton component is usually implemented and stored within the Singleton class itself. This is achieved using a private static field that contains the single instance of the class, and a private constructor to prevent the creation of other instances. Access to this instance is provided through a public static method, for example, getInstance().

Example in Java:

public class Singleton {
    private static Singleton instance;

    private Singleton() {
        // private constructor
    }

    public static synchronized Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

Thus, the instance is stored inside the Singleton class, and the application accesses it through the static method. In more complex applications, Singleton can be integrated with a dependency container or framework, but the basic implementation is within the class.