Abstract: In order to further increase the benefit from application of CAD/CAM technology, it's necessary to transfer and exchange product data between different CAD/CAM systems. This paper gives a brief introduction to the short history of the development of IGES-the most widely used specification for product data exchange and its file structure. After discussing the functions of processors,the paper emphasizes a structure of IGES processor which is characterized by a portable nu cleus, thus minimizing the amount of work for developing processors. Finally, the paper discusses the entity relationships during transferring and exchanging product data,