In my last communique, I twice said Sketchpad when I meant Supposers.
In 1987, my student used the Supposer to discover the first theorem that anyone discovered in my class.
And it is the Geometric Supposer and GeoExplorer that do not allow dragging. The Geometer's Sketchpad does allow dragging -- and animation and recursion in scripts and much more. Eileen Schoaff Buffalo State College