The Apple Macintosh combined brilliant design in hardware and in software. The drawing program MacPaint, which was released with the computer in January of 1984, was an example of that brilliance both in what it did, and in how it was implemented.
For those who want to see how it worked “under the hood”, we are pleased, with the permission of Apple Inc., to make available the original program source code of MacPaint and the underlying QuickDraw graphics library.
(Via John Gruber.)
At that address you can download the MacPaint version 1.3 and the QuickDraw source code. Be sure to read the full page for some history and some very nice photos. Since John Gruber has already linked to the Computer History Museum site, the page might be slow to load or might not load at all. In that case, be patient and try later. I think it’s well worth it.