IgEs

IGES, short for Initial Graphics Exchange Specification, is a vendor-neutral file format designed to enable the transfer of product design data between computer-aided design (CAD) systems. It emerged in the 1970s and was standardized in the 1980s to improve interoperability among a wide range of CAD tools and vendors.

IGES data is stored as ASCII text arranged in 80-character records and organized into six sections: Start, Global, Directory Entry, Directory, Parameter Data, and Terminate. The Global section carries metadata such as units and author information. Directory Entry and Directory blocks describe each geometric or topological entity and reference the corresponding Parameter Data blocks, which actually contain the geometry and topology data. This structure allows representation of both geometry (points, lines, circles, arcs, splines, and surfaces) and topology (wires, shells, faces) necessary to describe parts and assemblies.

The format supports two- and three-dimensional data and is capable of encoding a range of geometric representations, making it suitable for exchanging CAD models between different systems. IGES files are typically saved with the .igs or .iges extensions, and the format is commonly distributed as text, though some variants exist in binary form.

Although IGES served as the de facto standard for CAD data exchange for several decades, it has largely been superseded by newer standards such as STEP (ISO 10303). Nevertheless, IGES remains supported by many CAD programs, and conversion tools continue to facilitate legacy data exchange, preserving its role in the history of computer-aided design interoperability.