The "SAT Operating System" is an app (program) for your TI-84+ C Silver Edition graphing calculator that you use during the SAT test. All of the equations you will ever need during the SAT test (mathematics sections) are available to you a simple, fast, and easy-to-use interface. You can increase your SAT score by 60 points and often more just by using this software. With the SAT Operating System, it is now possible to make calculations more quickly and with greater accuracy than would normally be possible if you tried to solve math problems by hand. Now you might think, "but I'm really good at math. Why would I need this software?" The answer is: you need it because the SAT test is all about TIME. Sure, you know the approach to the problem and you know the equations needed, but how fast can you make those calculations by hand and what if you make a mistake in setting up your equation? With the SAT Operating System for your graphing calculator, you won't have to worry about time or making mistakes during the test. Plus, installing the software on your calculator only takes 5 minutes.