We can also use the page headers to store information like the deleted bit. An even better solution Save that thought for after we've covered B-trees. B-trees Balanced trees. The keys define intervals in the key-space and the pointers point to the records in those intervals. If the internal nodes contain data, the tree is a B-tree.
Splits can propagate upward to the root.
Reverse splits On delete, could empty a page. Like splits, reverse splits can propagate to root. Need to map the nodes to pages. Pointers are page numbers. If you keep full keys at every point, you end up storing the same strings repeatedly.