These limited changes meant that the original Macintosh system remained largely as it was when initially introduced. This initially shipped in three volumes, adding another to describe the changes introduced with the Mac Plus, and another for the Mac II and Mac SE. Some perspective on the scope of the changes can be seen by examining the official system documentation, Inside Macintosh. The development of the Macintosh system software up to System 6 followed a fairly smooth progression with the addition of new features and relatively small changes and upgrades over time.
