You need to hit "Return" after entering anything in the text box at the
bottom in order to set it.

Note that this program uses different insertion and deletion algorithms.
Unlike our text (which makes a single pass down the tree), they go down
the tree to insert or delete and then go back up the tree, performing fixup.
The "Lecture on Btrees" link gives a very brief description of the algorithms.

Note also that what they call the order is the maximum branching order, i.e.
what we call 2t (our t is the minimum branching order).  So if you want to
make trees like those in Figures 18.7 and 18.8, you should enter 6 in the
Order/Reset text field (and hit "Return" to set it).  After you have set
the order, you can either be in Insert or Remove (what we call delete) mode,
then successive inserts or deletes can be made by typing in the bottom
text field (and hitting "Return" after each one.  In "Tutor" mode you will
be prompted for where to put items or how to reconfigure the tree.

Doug Dunham
 
-- 
Doug Dunham				Phone: (218) 726-7510
Dept. of Computer Science, UMD 320HH	FAX:   (218) 726-8240
Duluth, MN 55812-2496 USA                    
Email: ddunham@d.umn.edu		Web: http://www.d.umn.edu/~ddunham/