Two different builds of each NT-based operating system exist:
- The (or ) of Windows is the end-user version of the operating system. The system and drivers are built with full optimization, debugging asserts are disabled, and debugging information is stripped from the binaries. A free system and driver are smaller and faster, and it uses less memory.
- The (or ) of Windows serves as a testing and debugging aid. For details, see checked build.
Distribution media containing the free build of the operating system do not have any special labels -- in other words, the CD containing the free build will just be labeled with the Windows version name, and no reference to the type of build.
The first opportunity to handle an exception. If an exception is not handled by any handler on the first opportunity, the handlers are given a second chance.