When choosing the control (2D or 3D) and format (OCX or DLL) for your applications, it is useful to understand the functionality and relationship between the DLL and OCX format of each control.
The DLL control is the “charting engine” for both the OCX and DLL. It stores the internal values of the chart’s properties and performs axis calculations and all low-level chart functions. The OCX builds on this charting engine, adding a fully object-based API, support for OLE automation, persistence, and an end-user Property Editor. The following diagram illustrates this relationship.
