SAGE Air Defense System

The Semi-Automatic Ground Environment (SAGE) system was a massive computer network for air defense. It was one of the first systems to utilize CRTs and light pens for interactive data input and display, influencing future graphical interfaces.

Significance

Though not directly CAD, SAGE demonstrated the feasibility and power of interactive graphics, providing a crucial precursor to systems like Sketchpad and inspiring many early computer graphics researchers.