RPN-55 SD - An HP-55 Simulator for iOS Devices

RPN-55 — Extending the HP-55

What's been added in RPN-55

Selling for the same price ($395) as the HP-45 two years earlier, the HP-55 offered more registers, more conversions, and programmability. In addition, it featured the timer already implemented in the HP-45, but not made officially available to the user due to its pure accuracy and stability. The HP-55 solved this by adding a quartz-controlled oscillator.

RPN-55 SD enhances the HP-55 in many ways:

MEMORY	HP-55	RPN-55
Register Arithmetic	For STO operations on primary registers only	For both STO and RCL operations on all 20 registers, including the double-register ∑+ (R.1 and R.3) working with stack registers X and Y.
Volatility	Program and all registers lost on power-off	Program and all registers preserved ("continuous memory")

TIMER
Range	100 hours	12, 24, 100 hours
CLx key	Resets timer to 0	100 hr: Resets timer to 0 12/24 hr: Sets timer to actual time
ENTER key	No effect	100 hr: No effect 12/24 hr: Toggle date display

FUNCTIONS
r	Not available	Correlation coefficient
x̂	Not available	x-estimate for given y
ENG	Not available	SCI mode with exponent fixed to multiples of 3
ABS	Not available	Make X value positive
INT	Not available	Integer part of X
FRC	Not available	Remove integer part of X
RND	Not available	Round X to displayed value
RAND	Not available	Create fractional or integer random number, as defined in Settings
P≷S	Not available	Swap primary and secondary registers


*FUNCTIONS (with setting Replace Unit Conversions* set to ON)**
sinh, sinh^-1	Not available	Hyperbolic sine and inverse
cosh, cosh^-1	Not available	Hyperbolic cosine and inverse
tanh, tanh^-1	Not available	Hyperbolic tangent and inverse
LOGy	Not available	Base y logarithm of x
LN x!	Not available	Logarithm of factorial of x
∆%	Not available	Percent difference from y to x
%∑	Not available	x as percentage of register ∑x
PUSH	Not available	Saves the entire stack on a 4-level stack
POP	Not available	Replaces the stack with the last PUSHed values (0 if none)
UNITS	Not available	Temporarily reveals the unit conversions until one of them has been executed. This also works as part of a program.
PSE	Not available	Pauses program execution for one second.

PROGRAMMING
Capabilities	49 steps Editing by replacing steps	99 steps Insert and delete steps with automatic address correction
Clear Program	Not available	Yes, with user confirmation
Clear Program Range	Not available	Clear any block of steps with automatic address correction
Delete f or g key	Cumbersome	Yes, by entering f or g again

USER INTERFACE
Prefix keys	Active if pressed	Active if pressed. Deactivated if pressed again. Indicators show state.
Register view	Not available	All registers shown on single screen including formatted display. Run/Stop and single-step program without leaving register view. Store and recall split times by tapping split number.
Decimal Point, Thousands separator	Fixed to decimal point (DP). Thousands separator not available	User-selectable, DP or comma. Thousands separator optional
Angular mode indicator	Not available	When not DEG, mode is shown in the top-left corner of the display.
Command display	Not available	In program mode or while single-stepping, current command is shown as text below display
Current step number display	Not available	Current program step number is optionally shown below display
Program memory fill status	Not available	Red progress bar shows amount of program memory filled
Low battery	Lights all decimal points	Lights all decimal points in vintage mode. Lights a small red indicator in extended mode. (When iPhone charge < 10%.)

Switching to timer mode with x = 43.170992:

1. Vintage mode (100-hr only)

2. Extended mode 100-hr:

3. Extended mode 24-hr:

4. Extended mode 12-hr:

5. Date with weekday number:

6. Date with localized weekday name

			Importing Numeric Data

			You can preset RPN55's registers with data created externally without having to type them in.
			Simply prepare the data in text format in any app that can handle text, like Notes, Mail and many others.

			The data format looks like this:
			Rn or R.n value (where n = 0…9)

			Example: To set R1 = 4.5, R6 = 6.28E-7, R.3 = 439, prepare your data like this:
			R1 4.5 R6 6.28e-7 R.3 439
			Select all of the text and paste.

			Notes: Upper-/lower-case is ignored. One or more blanks or tabs may follow the register number. M may be used in place of R. R.n may also be written as R1n, e.g. R.3 is the same as R13. The order of the registers is irrelevant. Unlisted registers are left untouched.

			Extra Functions

			r
			Calculates the correlation coefficient for a linear regression. Note that the method shown on page 61 of the Owner's Handbook calculates coefficient of determination, which is the square of r.

			ABS
			Sets x to the positive value of x.

			INT
			Sets the fractional part of x to 0.

			FRC
			Sets the integer part of x to 0.

			RND
			Rounds x to the value currently shown on the display.

			RAND
			• If the RAND setting is Off: Creates a random number between 0 (incl.) and 1 (excl.). • If the RAND setting is On: x ≤ 0: creates an integer random number in the range 0…2³²–1. x > 0: creates an integer random number less than x, but no larger than 2³²–1.

			P≷S
			Swaps registers R0…R9 with registers R.0…R.9.

			LN x!
			Calculates logarithm of factorial. This function allows handling factorials of very large numbers, as may occur in statistical computations. By using the logarithm of these factorials, multiplication and division are reduced to addition and subtraction. On return: x = LN x! y = mantissa of x! z = exponent of x! (assuming x! = y·10^z) z+1 = number of digits of x! x may be any positive number up to 4.4673259 × 10⁹⁷.

			∆%
			Calculates the percent difference between y and x. The stack doesn't drop.

			%∑
			Calculates the percentage x is of the value in the ∑x register (R.1)

			PUSH
			Copies all four registers of the stack to an internal stack of stacks. Four levels are available.

			POP
			Retrieves the latest PUSHed copy of the stack. The current x value is saved in LastX. The oldest copy of the stack is copied down on the internal stack. NOTE that CL.R clears the stack of stacks, while CL R does not. You can use P≷S CL R P≷S to clear the secondary registers without affecting the stack of stacks.

			UNITS
			Example: Calculate the base 2 logarithm of 5 inches converted to millimeters. 2 ENTER 5 f UNITS g in➞mm f LOGy Result: 6.99 This sequence also works as part of a program.

			PSE
			Executes a one-second pause. A green indicator lights up while the pause is active.

			Timer

			Operation
			When you switch to timer mode, the current value of x is taken as the starting time. If the value is an invalid time, 0 will be shown. Invalid starting times are negative numbers, or times equal to or larger than 100 hours (or 24 hours), or more than 59 minutes in the minutes field, or more than 59.9999 seconds in the seconds field. When leaving timer mode, the actual mode switching doesn't occur until the timer has been stopped by R/S.

			R/S
			Press key to start and stop the timer. This also works in register view.

			CLx
			100-hours mode: resets the time to zero. 12 and 24 hours: sets the time to the current real time.

			EEX
			Shows or hides the hundredths digits.

			ENTER
			Toggles between date and time display. Date separators blink while the timer is running. Split times may be stored, but not recalled, while the date is shown. Weekdays follow the ISO rules where Monday = 1, Sunday = 7.

			Split Times
			Pressing any digit key 0…9 while the timer is running stores the current time in the corresponding register. Pressing any digit key 0…9 with the timer stopped retrieves the stored time from the corresponding register, except when the date is shown. In register view, press any split time instead. Non-zero values are highlighted in extended mode. Split times are still available after leaving timer mode.