Most automated assembly systems currently in use in the aeronautical industry utilize ISO code to support assembly programming. However, ISO code which serves a valuable function for NC milling machines, has a number or drawbacks when applied to assembly process including: Post processors are machine dependent, requiring significant reprogramming to accommodate elemental cell configuration differences or changes. ISO code is not user-friendly Programming modifications demand programming expertise, are beyond the capabilities of the machine operator, and are tedious and time consuming. The lack of program structure leads to difficulties in comprehension for operators. Then, in order to reduce programmer work and to simplify and secure operator interface, the CTRI Robotics Division of DASSAULT-AVIATION decided to design PEGASUS environment which offers powerful programming, cell control features and user-friendly Man-Machine Interface.