A file with .igs (Initial Graphics Exchange) extension is a 2D-3D design exchange file format that is independent of source or destination file format specifications used by CAD applications. It is used to exchange design information about circuit diagrams, wireframes, the freeform surfaces between two independent systems. IGS files can be opened by applications such as Autodesk, FreeCAD, CADEX CAD Exchanger, and other similar applications.
PPS, PowerPoint Slide Show, files are created using Microsoft PowerPoint for Slide Show purpose. PPS file reading and creation is supported by Microsoft PowerPoint 97-2003. The more latest version of this file format is PPSX which is based on Office OpenXML standards. PPS files can still be read by latest versions of Microsoft PowerPoint, but newly created files can only be saved in PPSX file format. When a PPS file is shared with another user and opened, it starts as Powerpoint show unlike PPT file which opens in editable mode.
You can also convert IGS into many other file formats. Please see the complete list below.