There are many inexpensive scientific calculators on the market, but few boast the two-line display and other advanced features users get with the TI-30x IIS. The display 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 in any way you like for a recalculation. Better still, 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 you solved two minutes ago, two days ago, or whenever.