AutoLISP has been in AutoCAD for a long time, well before my time when I started with AutoCAD R12 for DOS in 1994. At its core, AutoLISP really has not changed much in the past 15 years outside of the introduction of Visual LISP and the ability to utilize the ActiveX API on Windows.
There were a few additions to the Visual LISP extension in AutoCAD 2013 which expose some new functionality from the ActiveX API and a few new functions that allow you to obtain the Machine and User product keys of AutoCAD. Along with some new functions, there are some new variables introduced as a result of new constants being added to the ActiveX API.
To use the the changes made to the Visual LISP extension, be sure to call the VL-LOAD-COM function first.
VLA-GET-ACTIVEINVPROJECT / VLA-PUT-ACTIVEINVPROJECT - Specifies the active Inventor project being used by the Model Documentation feature. (Internal Use Only)
VLA-GET-INTENSITYCOLORSCHEME / VLA-PUT-INTENSITYCOLORSCHEME - Specifies the color scheme to use for displaying intensity values.
VLA-GET-SHOWCLIPPED / VLA-PUT-SHOWCLIPPED - Enables or disables the clipping boundary.
VLA-GET-SHOWINTENSITY / VLA-PUT-SHOWINTENSITY - Specifies if the point cloud is displayed using a shaded color scheme.
VLA-PUT-LENGTH - Sets the Length property for a point cloud.
VLAX-MACHINE-PRODUCT-KEY - Returns the AutoCAD product key from the Machine hive in the Windows Registry. (ie. "Software\\Autodesk\\AutoCAD\\R19.0\\ACAD-B001:409")
VLAX-USER-PRODUCT-KEY - Returns the AutoCAD product keyfrom the User hive in the Windows Registry. (ie. "Software\\Autodesk\\AutoCAD\\R19.0\\ACAD-B001:409")
VLAX-PRODUCT-KEY - While still supported, it is recommended to use the new function VLAX-MACHINE-PRODUCT-KEY instead which returns the same value.
ACNATIVE = 60
AC2013_DWG = 60
AC2013_DXF = 61
AC2013_TEMPLATE = 62
ACINTENSITYBLUE = 4
ACINTENSITYEDITABLEFLAG = 5
ACINTENSITYGRAYSCALE = 0
ACINTENSITYGREEN = 3
ACINTENSITYRAINBOW = 1
ACINTENSITYRED = 2
ACTRUECOLOR = 0
ActiveX API Changes in AutoCAD 2013
***Updated 7/10/12 to include the change to VLAX-PRODUCT-KEY.