The first pair of diagrams is for “p1 = p2;”. Before: A box at left labeled p1 points to a box containing 84 at right; a box labeled p2 at left points to a box containing 99 at right. After: Same diagram, except both p1 and p2 now point to 99.

The second pair of diagrams is for “*p1 = *p2;”. Before: Same as the “before” diagram in the first pair. After: Same as the “before” diagram, except both of the numbered boxes now contain 99.