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It's difficult to explain why Improv was so revolutionary, so here is a piece from a Lotus marketing video to help you understand why it was such a revolution.

Now some 23 years later I am aware of only one product which approached what Improv could do, and that is
Quantrix Modeler (another NextSTEP derivative) which is available on Mac OS X and recent Microsoft OS offerings.

Improv Sales Video
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