The 401 uses the built-in cam stack for zig zag and some of its decorative stitches. There are also additional decorative stitches available, but require additional, external cams.
This site has some great information about the 400 series of machines:
http://blog.sew-classic.com/2008/10/...ne-review.aspx
Here is a comparative list of the stitches that the 401 & 403 machines can make. (note: the 403 uses only the external cams)
http://i522.photobucket.com/albums/w...atterns401.jpg