By default, it should be at ..\include\CPPAPI. But on my machine this folder doesn't even exist, only 'CatIDs' and 'GridIDs' folders reside in \include. I've installed ArcGIS Desktop 9.3 and its VC++ SDK.
I am new to ArcGIS and LiDAR, I've got LAS file and corresponding text version, all I need to do is to convert txt file to shp file. I found one example code that can do this, it included ArcSDK.h.
Thank any of you for help.
I believe you want to install the ArcGIS Engine C++ Dev Kit (ArcGIS Engine SDK for Cross Platform C++) described at http://wikis.esri.com/wiki/display/ag93bsr/ArcGIS+Engine#ArcGISEngine-DeveloperSolutions%28SDK%29Requirements. I don't use the VC++ Dev kit so I'm not sure if it includes the ArcSDK.h file. However, if you install ArcEngine Runtime and the ArcEngine SDK for cross platform C++, the ArcSDK file will be in ArcGIS\include\CPPAPI as you noted.