This document provides standards for describing steel structure pieces in numerical control files. It outlines:
1. The document replaces all previous versions and was edited by 10 engineers.
2. It establishes a common coordinate system and conventions for describing piece geometry like holes, contours, markings, and cuts to enable translation between CAD files and numerical control programs.
3. File names for the interface are composed of a meaningful name indicating the drawing and piece number, followed by a ".NC" extension of up to 3 characters. This standardized interface aims to make descriptions neutral and compatible with any numerical control machine.