RPN-55 SD 2.9

RPN-55 SD is a photo-realistic simulation available for the iPhone, aiming to recreate Hewlett-Packard's HP-55 programmable scientific calculator from the mid-1970s. This particular model, part of HP's renowned calculator series, was known as the "Merlin" and was priced at $395 during its production period from 1975 to 1977. HP advertised it as having more pre-programmed functions than any other handheld scientific calculator at the time.

One of the standout features of the HP-55 was its crystal-controlled 100-hour digital timer, possessing the unique capability to store and recall times while the timer was in operation. The RPN-55 SD simulation keeps this functionality intact, adding the ability to serve as a 12-hour or 24-hour clock with date and weekday display options.

The simulator faithfully replicates the operation of the original calculator while offering enhanced speed and doubled program memory capacity. In addition, users can activate extended features to further enhance their experience with the simulation.

RPN-55 SD includes a range of features such as vintage and extended modes, programmability with conditional branching, subroutines up to four levels deep, 20 registers for arithmetic operations with live view capabilities, program listing view, and library view. Users can store and retrieve multiple programs, utilize a 100-hour timer with clock modes and split time functionality, swap unit conversions paired with additional functions like hyperbolics, and share content through various methods such as email, AirDrop, Dropbox, copy-paste, and printing. The simulator comes pre-loaded with an extensive library of 112 programs spanning different functions and calculations.

In terms of calculator functions, RPN-55 SD incorporates features like statistics (including linear regression and correlation coefficient calculations), trigonometric functions in degrees, radians, and grads, polar/rectangular conversions, basic math operations (inverse, square root, logarithm, exponential functions), storage arithmetic (store and recall operations), percentage calculations, factorial computation, random number generation capability, unit conversions, and more.

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