Usually one think of a component as something to use and to call. In some cases components need to execute something on your application. some methods are common:

	Callback. The component request you to provide some procedures. Prototype of theses procedures are strictly defined. Depending of the system you can provide them as pointer to procedures, specially named functions or linked list in global area. A common example is the system itself. It is required that a program supplies a main() procedure.
	Subclassing: The component define a class or an interface with some virtual methods. You are requested to implement theses methods in a subclass and you supply objects of this subclass to the system. A good example of this is the MFC Microsoft Foundation Classes. Another good example is the handling of attributes. You maintain objects called attributes attached to the component. The component will call them all on various occasions.
	Messaging. The framework expect some kind of message loop to be pooled by your application.
	Event and connection points. This last technique is employed in the COM model. A component publish a well known interface. If you implement this interface in an object of your application and connect this object to the component you will receive the events from this object.

This is really the most basic way to share software. You get it, adapt it to your environment, compile it and finally use it. Poor maintenance. If the language is portable like C you will gain a high portability. The drawback is that you will a poor integration with the environment and low level interface ( persistence, graphic, etc.;)

code based on a separate documentation. No check is made that the documentation is relative to the exact object module you use. Another disadvantage is that this particular release is statically bind in your code. . You bind it within your code and call any feature from your code.

A very specific case of dynamic library for Visual Basic is called VBX. Theses libraries are more self described than a normal dynamic library. It opens the way to self documented components. It has be replaced by Microsoft by the OCX.

Service. Inter Process Calls there are at least two programs one calling the other. This solution need some support from the operating system like: socket, shared memory, rpc, DDE, etc.. Usually this solution will be wrapped in a light library hiding the communication process. The applications don't share the same memory space and they might even be on different computers. A major benefit is that the CADCAM system will stay far from the application giving the author a feeling of security and stability.