Extended ArcGIS by creating Java, C++, or .NET extensions that plug seamlessly into ArcObjects components.
ArcGIS is built from an integrated collection of extensible software components called ArcObjects. The ArcObjects framework can be extended by integrating external data sources and leveraging external libraries with ArcObjects extensions, all of which plug seamlessly into ArcObjects components and can be consumed by ArcGIS Desktop, ArcGIS Engine, and ArcGIS Server applications since they are built from ArcObjects.
Extend ArcGIS by creating Java extensions that plug seamlessly into ArcObjects components.ArcObjects for Java
Extend ArcGIS by creating .NET extensions that plug seamlessly into ArcObjects components.ArcObjects for .NET
Embed GIS functions into existing applications and build focused custom applications that deliver advanced GIS systems to many users.ArcObjects for C++