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.
Files with ICO extension are image file types used as icon for representation of an application on Microsoft Windows. These come in different size, colour support and resolution to suit the requirements of the display. Another similar image file format on Microsoft Windows is .CUR for cursor representation and defines a hotspot in the image header. On MacOS, ICNS file formats serve the same purpose as ICO files. Several online websites as well as applications provide the feature of creating such files and convert other image formats such as BMP, PNG, etc. to icon file format. The official IANA registered Internet media type for ICO files is image/vnd.microsoft.icon.
You can also convert IGS into many other file formats. Please see the complete list below.