 IBM and Hazeltine were selected to develop the mission computer and display system.The IBM computer was designated 4PI, and the software was written in JOVIAL.A Semi-Automatic Ground Environment (SAGE) or back-up interceptor control (BUIC) operator would immediately be at home with the track displays and tabular displays, but differences in symbology would create compatibility problems in tactical ground radar systems in Iceland, mainland Europe, and South Korea over Link-11 (TADIL-A).