||STEP 3D CAD File
||Standard (developed by International Organization for Standardization)
||★ ★ ★ ★ ★ Popular
3D assembly file containing three-dimensional object data; supported by various mechanical design programs as a 3D product model data exchange format.
STP files are saved in a text-based ASCII format that conforms to the STEP Application Protocols ISO 10303-2xx.
Dassault Systemes CATIA
||August 29, 2013
Information from the PC File Extensions Reference