The iPad uses the split view controller when in landscape mode so you can display the lists of calculators, History, List Manager, Options, Styles and Documentation along side of the calculator.
When in portrait mode, you can do a right swipe just above the "CALC 1" key to display the lists or navigate to another calculator. You can also right swipe the display area to load the next calculator.
You can also bring up CALC 1 in Slide Over mode in devices that support this feature.
Some iPads also support a split view that will display CALC 1 and another app side by side.