Turn on the Super-45 mode and you'll convert your HP-45 into a calculator made for the 21st century. (Note that RPN-45 SD always operates in Super-45 mode.)

In Super-45 mode, RPN-45 shows the features of the printing desktop model HP-91, enhanced by a large number of additional functions.

• Complex numbers. Almost any function or operation may be performed on complex numbers. This includes storing and retrieving numbers using all nine registers, as well as doing register arithmetic on them. And unlike many implementations, the stack's size remains unchanged at four levels. Verify both the real and the imaginary part of your numbers anytime by calling up the register view. Users familiar with the HP-15C will feel right at home with these features. Refer to example 10 under "Examples" to see how it works.


• More memory. In addition to the standard registers R1 thru R9, you get nine more registers (R11 thru R19). And all registers (stack included) are non-volatile – their content will not be lost when you exit the application, or even when you shut down the iPad completely. In portrait display, a single tap on the register view lets you switch between normal and extended registers. You may swap each register with its extended counterpart, even all at once. And last but not least, register R9 will never be cleared by trigonometric functions.


• New functions. Use hyperbolic functions and their inverse. Easily solve linear equations in two or three unknows, as well as quadratic and cubic equations in one unknown. All solutions are presented, even the complex ones. The function Prob computes the normal (or Gaussian) distribution. L.R. determines the regression line and the Pearson correlation coefficient of a number of paired variables. Estimates for x and y are just a tap away. Calculate the weighted mean and its standard deviation, determine permutations and combinations. Generate random numbers in a given range. Find the integer part or the fractional part of a number. Round a number to the value shown in the display. Finally, DATE gives you the day of the week of any date between Jan 1, 0001 and Dec 31, 9999, both for the Julian and the Gregorian calendar. In addition, you may retrieve the date and day of the week of any date a number of days from a given date. You also get the number of days between any two dates, even on 30-days per month basis. Retrieve the entire stack following an operation. Show the integer part of the display value as hexadecimal value. Or get the display value as percentage of a sum built using the Σ+ key.


• Enhanced functions. Computing the factorial is not restricted to natural numbers. Raise any number to any power. Get logarithms and square roots of negative numbers. Use arguments >1 or <-1 for arcsine and arccosine. Get the mean and the standard deviation of both x and y values at the same time. Use STO Σ+ and RCL Σ+ to directly store and retrieve real or complex 2-dimensional values in R7 and R8, even apply register arithmetic on them. Extend the timer's range from 12 to 100 hours. And synchronize the timer with the your device's clock by simply tapping T. Use the timer as a chess clock. Display values in ENG (engineering) format.


• Enhanced user interface. Prefix keys like FIX, STO, RCL, HYP, EEX, or the gold key are clearly marked when activated. Tap them to deactivate. Never wonder again what angular mode the calculator is currently in – the active mode is highlighted by an underline. The last used decimal point setting is stored permanently (optionally the RPN-45 HD). Results which are too small for the current display setting are not shown as 0 anymore, but automatically make use of the scientific display mode. Finally, RPN-45 will warn you when you try to enter a value using the summation key Σ+ and the current entry count is not a natural number.
  

• Printer. The built-in printer turns RPN-45 into a super-charged HP-91 (sold for $425 in 1976).