The ACIS file format, identified by the '.acis' or '.sat' (Standard ACIS Text) extension, is a geometric modeling kernel developed by Spatial Corporation (now part of Dassault Systèmes). It's a widely used format for representing 3D solid models in CAD (Computer-Aided Design), CAM (Computer-Aided Manufacturing), and CAE (Computer-Aided Engineering) applications. ACIS files store precise geometric information, including surfaces, curves, and solids, along with topological relationships between these elements. This allows for accurate representation and manipulation of complex 3D shapes. The format supports a variety of geometric primitives, such as lines, arcs, splines, and NURBS (Non-Uniform Rational B-Splines), enabling the creation of intricate designs. ACIS is known for its robustness and reliability in handling complex geometric operations, making it a popular choice for professional engineering and design software. The format is often used for exchanging 3D model data between different CAD systems, ensuring interoperability and facilitating collaborative design workflows. The binary format is '.sab' (Standard ACIS Binary).