RPN-55 SD is the first photo-realistic simulation for the iPhone of Hewlett-Packard's low-cost alternative to the famous HP-65 programmable scientific calculator. Produced from 1975 through 1977, it was the "Merlin" member of the classic HP calculator series, priced at $395. HP claimed that it featured "(...) more pre-programmed functions than any other scientific pocket calculator in the world."
A main feature of the HP-55 was a crystal-controlled 100-hr digital timer with the ability to store times while the timer was running and later recall them. On RPN-55 SD the timer may also act as a 12-hr or 24-hr clock.
While the simulator works just like the original calculator except being much faster and having twice the program memory you can turn on extended features to make it even more enjoyable to use.
RPN-55 SD comes with original HP programs built right into it.
Vintage mode or Extended mode
Programmable (99 steps), conditional branching
Insert and delete steps with automatic address correction
Delete range of steps
Subroutines (4 levels)
20 registers, "continuous", with unrestricted store/recall arithmetic
"Live" register view
Program listing view
Program library view
Store and retrieve any number of programs
100-hr timer supporting 10 split times and 12/24-hr clock mode
Swap unit conversions with additional functions, e.g. hyperbolics
Sharing: e-mail, AirDrop, Dropbox, copy, paste, print
Almost 100 programs pre-installed
Statistics (linear regression, mean, standard deviation, correlation coefficient, x- and y-estimates)
Trigonometric functions (degrees, radians, grads)
Inverse, square root, logarithm, exponential, pi
Storage arithmetic (store and recall)
Percent, absolute, integer, fractional value, round
Unit and hours conversions