A Component diagram describes logical components that make up the system.
A Component contains information about the logical Class or Classes that it implements, thus creating a mapping from a logical view to a component view. Dependencies between the Components makes it easy to analyze how a change in one component affects the others. The Components may also be shown with any of the Interfaces that they expose. They, as with almost any other model elements, can be grouped into Packages, much like Classes or Use Cases.
The Component diagrams are used in the later phases of the software development, when there is a need to divide up Classes among different Components. When working with the CASE facilities, the Components are used for file-class mapping during code generation, reverse engineering, and round-trip engineering operations.
As of MagicDraw 17.0.1, the Component diagram (or the Deployment diagram) replaces the Implementation diagram, which is no longer supported in UML standard. An Implementation diagram created with earlier versions of MagicDraw, now opens as
Deployment diagram, if Nodes were used in the Implementation diagram
Component diagram, if Nodes were not used in the Implementation diagram
Customized diagrams that were based on the Implementation diagram are now based on the Component diagram.