There are a wide range of APIs (Application Programming Interfaces) that are available for creating custom applications in AutoCAD. Which API is right for you depends greatly on your experience and the time you can commit to learning, but for many the first API that they are ever exposed to is AutoLISP because of its ease of use and the sheer number of programs that are available for download from the Internet.
AutoLISP allows you to channel your knowledge of AutoCAD commands, and begin to combine them in ways that you might have never thought possible or maybe you have and that is what kick started your interest in programming. Where you go from there is often different for many. Many simply learn AutoLISP and that is enough for them to improve the tasks that they perform on a daily basis. For others, AutoLISP is simply a stepping stone towards Managed .NET or even ObjectARX.
The available AutoCAD APIs are:
- Transmittal (eTransmit/Archive)
- Sheet Set Object (Sheet Set Manager)
- CAD Standards Plug-in (CAD Standards and Batch Standards Checker)
- Connectivity Automation Object (dbConnect)
- Managed .NET
The documentation for all of the available AutoCAD APIs can be located under the AutoCAD Developer Center. Based on which API you want to work with, you might find that some of the documentation is available through the product's help, installed locally with the product, or available with the ObjectARX SDK.