IGS, also known as IGES, is a vector graphics format that is typically used by CAD (Computer-aided Design) software for exporting vector data. IGS Viewer can help you explore this type of files without needing to install any complex CAD utility.
The application does not require a lot of RAM or CPU power in order to run at full performance, so even if you are working on a rather old PC, you should not encounter any issues in running this application as long as you install Microsoft .NET Framework.
The graphic interface is intuitive so that if you have worked with CAD programs in the past, you should have no problems in correctly interpreting the pictograms within IGS Viewer - that is, if you do not have the patience to read the captions that appear when you hover the mouse over them.
You simply need to open an IGS file and start moving and rotating the model as much as you need, turn it into wireframe or disable the shading. Each of these actions can be completed by pressing the corresponding button on the statusbar of the main window of the app.
Alternatively, you can also get to the same results by using solely the mouse buttons and the keyboard, so if want to save time you can learn the correct keyboard combinations and complete tasks much faster.
As this is a viewing application, you will not be able to modify your 3D model in any way, but you can still change its color or adjust the zoom level if these help you analyze it better.
Overall, IGS Viewer is a tiny application that can help you explore IGS files even if you do not want to install CAD tools on your PC. It allows you to move and rotate whatever 3D model you might select.