The Texas Instruments TI-30X IIS 2-Line Scientific Calculator features a two-line display and other advanced features that users get with the TI-30X IIS. The screen shows the equation you are creating on the top line and the numbers or symbols you are currently entering on the second line. Once the equation is solved, the results are displayed on the second line, and you can use the four arrow keys on the front of the calculator to edit the original equation any way you want for a new calculation. Better yet, pressing the up arrow repeatedly lets you browse through a cache of dozens of previous calculations, meaning you can look back to see the answer to a problem. The device uses solar power when possible, but can fall back on the internal batteries (which are included) if there is not enough light. There are three angle modes (degrees, radians, and degrees), scientific and engineering notation modes, and even one- or two-variable statistical modes. Five variables can also be assigned to their own memory slots. The calculator comes with a snap-on cover that fits on the back of the device. Key Features: Two-line display Fraction features Conversions Basic scientific and trigonometric functions Edit, cut and paste entries Solar and battery powered One- and two-variable statistics Ideal for: General Mathematics Pre-Algebra Algebra 1 and 2 Geometry Statistics Science in general