PEMDAS is an advanced scientific calculator with an easy-to-use interface for doing calculations with equations and variables. It is the touch version of PEMDAS Widget, an Apple Design Award winning Dashboard Widget.

In addition to the keypad, it also features a History tab, which displays all the equations in the current session, and provides one tap access access to duplicating equations or using their associated results. PEMDAS auto-assigns variables to all calculations, which you can access in the Variables tab. You can clear the session by tapping the clear button in the History or Variables tab, or by pressing and holding the clear button in the Keypad tab.

In addition, PEMDAS lets you switch between degrees and radians, and has support for percentages, trigonometric, hyberbolic, and logarithmic/exponential functions. You can also convert between hexadecimal, octal, binary, and decimal. PEMDAS lets you format the answer in scientific and engineering notation, has a preference for thousands separators, and lets you limit the amount of significant figures or decimal places displayed.

The website link below contains additional information and also screencasts of PEMDAS.