SketchPad SketchPad was the PhD. thesis of Ivan Sutherland, first published in 1963. SketchPad, a graphical manipulation system comprising both the necessary hardware and software, is recognezed as the first object-oriented system. SketchPad's accomplishment was twofold. First, SketchPad revolutionized the way that humans interact with their computers, utilizing a flat refreshing display that responded to a light pen. This natural mode of communication reduced the time necessary for a user to communicate his goals to the computer, and became (and continues to be) a fundamental influence on many following applications. Secondly, the internal workings of SketchPad introduce the notion of creating "objects," or instances of "classes" (although Sutherland did not name them as such), and manipulating formal properties of multiple instances of a class together with one command. These classes could even be abstract notions, called "constraints" in SketchPad. For example, a constraint of "Parallelism" could be represented as an abstract object and manipulated in SketchPad. The generic hierarchies of classes in the SketchPad system foreshadow those used in all OOPLs following. Furthermore, Wikipedia (the online encyclopedia) has this to say about SketchPad: "For a PhD thesis it is remarkably clear and readable." ;) Ivan Sutherland won the A.M. Turing Award in 1988.