RPN-65 - An HP-65 Simulator for iOS

Operation Modes of RPN-65 Pro

RPN-65 Pro supports four modes of operation which may be selected in "Settings".

Select any of the "Enhancements" listed below.

Off

RPN-65 simulates a real HP-65 as closely as possible. See HP-65 Peculiarities

Execution speed and display activity comparable to HP-65

Memory register R9 affected by operations as follows:
Set to y² on rect-to-polar conversion
Set to tan y on polar-to-rect conversion
Set to x value on comparisons
Set to tan x on sin
Set to 0 on arc sin
Set to cot x on cos
Set to 0 on arc cos
Set to 0 on tan
Set to 0 on arc tan

Can read data cards created by RPN-65 as well as RPN-67 and RPN-97

Use printer buttons to print x-value or program listing, or to trace program flow

Fast

Same as "Off", except execution speed is not slowed down to HP-65 speed.

UI

Same as "Fast", but with several User Interface enhancements added.

Step number and command name shown in W/PRGM mode

Print from calculator keyboard (not programmable):
Print space (blank line): f⁻¹ SPC
Print stack: f⁻¹ STK
Print registers: f⁻¹ REG
Print program: f⁻¹ PRGM
Print labels and flags: f⁻¹ LBL

Print x: f -x- is programmable

Prefix keys work as toggle keys with visual indicators

Trigonometric mode is shown in display

"Sticky" back-step key BST (tap g SST) in both W/PRGM and RUN modes. Tap g to release.

GTO.nnn command to jump to any program step

GTO.. command to jump to last program step

Display doesn't change to SCI mode automatically as long as x < 1E10

Program execution stops at step 100 if all steps are NOP

Read data cards

Plus

In this mode, RPN-65 Pro acts like a much improved HP-65.
Existing programs will run in most cases. Programs making use of
(possibly undocumented) peculiarities of the HP-65 may behave differently.

In addition to all features of "Fast" mode, you get:

Real subroutines supported by 8-level stack

GSB command which may be used with any label (enter f⁻¹ GTO)

999 program steps

User-defined function keys a...e (in addition to A..E)

120 labels (0..9, 00..99, A..E, a..e)

120 registers (0..9, 00..99, A..E, a..e), all supporting STO and RCL arithmetic

Extended registers (00..99, A..E, a..e) may be cleared by f CLX (not programmable)

R0 accessible for store and recall operations

R9 not used internally; STO 9 and RCL 9 stored as merged keycodes

Comparisons of x with 0.

Indirect STi and RCi (g STO and g RCL) using register number stored in register 8.
R8 = 0..9 addresses the internal registers R0..R9.
R8 = 10..14, 15..19 addresses the internal registers A..E, a..e.
R8 = 20..99 addresses the extended registers 20..99.

ENG display mode (enter DSP+n, n = 0..9)

PRINT STK / REG / SPC / PRGM / LBL commands are programmable

Read and write data cards

Program cards created in Plus mode may define the following settings
to be applied when loading the card:
• Flag 1 and Flag 2
• Display mode
• Trigonometric mode

Default user functions are restored on program clear, but don't occupy program memory

DSZ decrements values between -1 and +1.

Operation y^x accepts y = 0 (for x ≠ 0) and y < 0 (for integer x)

Program execution stops at step 100 if program memory contains only NOPs.
Program execution skips steps 101..999 if that range contains only NOPs.

NOTES
- Loading a Plus card will automatically set the calculator to Plus mode
- Leaving Plus mode with Plus card inserted will eject the card
- Convert Plus cards to standard cards(or vice versa) by duplicating the card
- If not in Plus mode, underflow will halt a running program. Tap R/S to continue.

111 Additional Registers

In addition to the HP-65's regular 9 registers, you may use R0, registers A..E and a..e, and registers 00 through 99.
Full store and recall register arithmetic is supported.

Extended registers may be accessed just like regular registers by prepending their address with a decimal point.

Examples:

RCL f D	Get value of lower-case register d into X
STO.48	Store x in extended register 48

Registers may be printed out by the PRINT REG command (f⁻¹ REG) in modes UI and Plus.
Extended registers 00..99 are only printed when the paper tape printer mode is set to TRACE.

Extended registers 00..99 may be cleared by the command f CLx.
Registers A..e get cleared by the command f REG, along with the regular registers.

Note that f CLx may not be programmed by simply tapping the two keys in W/PRGM mode, as this would clear the program memory. Instead, enter the two keycodes – 31 and 44 – directly into the program listing in RUN mode. Alternatively, you may type the command name CLXT or CLEXT.

Another solution is to enter this key sequence (in W/PRGM mode):
f EEX CLx g BST DEL

Unlimited Register Arithmetic

RPN-65 Pro removes the HP-65's limitations on register arithmetic functions.

Register arithmetic supports both STO and RCL operations and works with any register (0..9, A...E, a..e, 00..99).

Examples:

RCL–7	Subtract value in R7 from X
STO.41	Store X in extended register 41
STO+.07	Add X to extended register 07
STO×E	Multiply X into register E

Saving the Entire Stack

The command STO ENTER ("STO STK") copies the LastX register as well as the stack registers X, Y, Z, T to extended registers R.00 through R.04 (in this order).
Likewise, RCL ENTER ("RCL STK") retrieves LastX and the stack registers from the extended registers.

105 Additional Labels

With 105 labels in addition to those built into HP-65, you'll probably never run out of labels again.

Available labels are: A..E, a..e, 0..9, 00..99.

Every label may the target of a subroutine call by using the GSB command (f⁻¹ GTO).

To address a 2-digit label, insert a "+" after the command, followed by the 2-digit label number.

Examples:

GSB 9	Execute subroutine at label 9
GTO f E	Go to lower-case label e
LBL+05	Define extended label 05 (note 2-digit number)
GTO+97	Go to extended label 97

In modes UI and Plus, label usage may be printed by f⁻¹ LBL (see picture at right.)

The location (or locations, if used more than once) of each label is listed, followed by the number of unused labels.
With extended labels 00..99 (Plus mode), only the first occurrence in the program is shown. Unused extended labels are not listed.

Note
There is a subtle difference between using A and GSB A to call subroutine A. While the former searches for the first occurrence of LBL A beginning at the top of memory, the latter searches from the next program step. This applies to all labels A..E and a..e.

Additional Flag Commands

RPN-65 adds handy toggle and test commands to the flag operations.
All commands are invoked by the prefix key DSP.

Command	Description
DSP f SF1 (or SF2)	Toggle flag 1 (or 2), then test if set
DSP f⁻¹ SF1 (or SF2)	Toggle flag 1 (or 2), then test if cleared
DSP f TF1 (or TF2)	Toggle flag1 (or 2)
DSP f⁻¹ TF1	Test if F1 is in the same state as F2
DSP f⁻¹ TF2	Test if F1 is not in the same state as F2

Using the Paper Tape Printer

RPN-65's paper tape printer emulates the HP-97's printer and adds a few twists.
The tape can hold up to 999 lines; older lines are dropped.

When using the printer, whether you are in MAN or NORM modes (where you must press Print x) or in TRACE mode (where RPN-65 automatically prints results), printed numbers can be shown in any display format – fixed point or scientific notation. By selecting the display format, you also select the print format.

Numbers that you key in – that is, numbers that are not the results of operations – are also printed. When you key in a number with the Print Mode switch set to NORM or TRACE, RPN-65 does not print it until you change display format or press a function key. Then the number is printed exactly as you keyed it in. A number that you keyed in is not the result of an operation, and no asterisks are printed to its right.

When you have keyed in a number, there is one time that the RPN-65 will change its format before printing. If you have specified fixed point notation and the number keyed in is also in fixed point format (i.e., you have not pressed EEX), RPN-65 will attempt to align the decimal points for easy readability on your printed copy. It will do this in fixed point notation by printing the number that you keyed in in the specified format (if the number can be printed without truncating), adding trailing zeros if necessary. This feature permits you to key in numbers in fixed point notation and line up the decimal points in the printed record of your calculations.

Printing Modes

RPN-65 supports the HP-97's MAN, TRACE, and NORM printing modes:

MAN
With the Print Mode switch set to MAN (manual), the printer is idle and does not print unless you press the Printx key or one of the other PRINT functions.

TRACE
With the Print Mode switch set to TRACE, the calculator prints numbers, functions, and intermediate and final answers, just as they are seen in the display. The results of functions are printed with the symbol *** to the right of the number .

NORM
With the Print Mode switch set to NORM (normal), the calculator records a history of the calculation sequence so that you can reconstruct your problem. In this mode you see digit entries and functions, but intermediate and final answers are not printed unless you press the Printx key.

When running a program in NORM and TRACE mode, RPN-65 also prints information about subroutine levels (see second screenshot at right.) The number at the left indicates the step where program flow will continue when the next RTN statement is encountered. No number means program execution will stop with the next RTN statement. Nested subroutines (available in Plus mode) are displayed by indenting the step number according to the nesting level.

To advance the printer paper, tap the paper advance button at the bottom. Hold the button down to advance several lines.

To quickly scroll to the beginning or the end of the printout, tap the arrow button at the top.

Program Listing

With the calculator mode switch set to W/PRGM, the paper tape printer's Printx button gets renamed to P Pgm.
With the calculator mode switch set to RUN in modes UI and Plus, you can use the PRINT PRGM command (f⁻¹ CLx).

The currently stored program will be printed as follows:

Print Mode switch set to MAN:
The printer lists step number, operation, and keycode for each step of program memory. The print range starts at the first non-NOP instruction from the current step and ends at the last non-NOP step in program memory (as defined by the current "Enhancements" settings.) All NOPs inside this range will be printed.

Print Mode switch set to NORM or TRACE:
The printer lists only the step number and instruction, omitting the keycode. This type of listing is useful for preserving a record of your program without the keycodes.
The start of the print range is defined as in MAN mode, but printing will stop on the third NOP in succession.

In Vintage mode, printing stops after each NOP command. The step counter is automatically increased, allowing you to step through program memory by repeatedly tapping the P Pgm key.

If Print Program is executed by a program, the listing starts with the first instruction in program memory not being a NOP.

Printing Display Value, Stack, and Registers

With the printer turned on and visible, commands like f⁻¹ REG, f⁻¹ STK and f -x- (available in UI and Plus modes) will execute much faster because values do not have to be shown on the display.

Changing the Ribbon Color / Printing Negative Results in Red

You may select a blue or black ribbon in Settings.
In addition, you specify negative results to be printed in red.

Editing the Paper Tape

Swipe left on a paper tape line to delete it. You can also insert an empty line above a line, or paste text created by the TXT button.

HP-65 Peculiarities

Back in 1974, the HP-65 was the first magnetic-card-programmable handheld calculator. Due to technical limitations, some characteristics seem rather odd in today's view. They did not appear in later calculator versions. As an example, notice that deleting step 100 of a program also deletes step 99.

It would make sense, for example, to assume that "one keypress = one program step". However, many 2-step instructions were merged into a single step, for example g NOP, g LSTx, STO/RCL 1 to 8 (but not 9!). In particular, the LBL function and the label name occupied two steps, which could lead to remarkable side-effects, especially when single-stepping and switching between RUN and W/PRGM modes.

A glaring deficiency was the absence of a back-step key. Single-stepping (SST) one or more steps too far by accident was best remedied by deleting and reinserting steps. Note that RPN-65 supports back-stepping in UI and Plus modes (press g SST).

If operated in vintage mode, RPN-65 faithfully simulates a number of these oddities. For example:

Sticky Minus Sign
Set the display to 0.00 (CLx)
Press the CHS key. The display shows -0.00.
Press the CHS repeatedly. The display never changes back to 0.00.

Cued Stops
It is sometimes helpful to put a familiar number into the X register before stopping for data. If a cue number is created as a program step immediately preceding R/S, it is not lifted into the stack and the number is overwritten by the data you key in.

default programs

recreate LBL E

(Hint: Use

in UI mode – or

in Plus mode – to quickly access step 96, enter the code, then return to mode "Off" or "Fast".)



001:  23        LBL   
002:  11        A     
003:  35        g     
004:  04        1/x   
005:  24        RTN   

006:  23        LBL   
007:  01        B
008:  32        f   
009:  09        √x    
010:  24        RTN   
...

097:  23        LBL   
098:  15        E     
099:  42        CHS    
100:  24        RTN

Cocked RTN
This refers to the fact that a RTN instruction not preceded by a call to the corresponding label is treated as NOP.

Example 1:
– Tap 5 A. The result is 0.20, as expected.
– Now enter 5  GTO A  R/S. You'll get 0.45 (=√0.20) because the RTN in step 005 executes as NOP.

Example 2:
– Address step 002 (by executing RTN W/PRGM SST RUN)
– Tap 5, then SST
   This will execute the subroutine A, found at step 001. The calculator dutifully executes the code (steps 003..006),
   then returns to the step following the call, which is 003.
   Since we're single-stepping, the program stops here to show 0.20. Tap SST twice to execute the remaining steps 003 and 004.
   The final result is 5.00.

Example 3:
– Clear the program memory (W/PRGM  f PRGM).
– Still in programming mode enter LBL A  1  +  RTN. Return to RUN mode.
– Clear the stack (f STK).
– Tap A. The result is 1.00, as expected.
– Clear the stack again, then tap RTN, then R/S (or GTO A  R/S).
– You'll get 2.00. The program ignores the RTN, then executes the 95 default NOPs to arrive at the top of memory, finally stopping
   at the RTN in step 5.

More operations to try out and explore:(RUN = switch to run mode, W/PRGM = switch to program mode)
(If you tried Example 3, restore the original sample program shown above first.)



   EXECUTE          |           DISPLAY           |   COMMENTS
____________________|_____________________________|_______________________________________
                    |                             |
   RUN 5 GTO E      |    5.00 W/PRGM        15-   |   Addresses step 99
                    |                             |
[Common start]      |                             |
1. RUN SST          |   -5.00 W/PRGM        42-   |   CHS
2. RUN SST          |   -5.00 W/PRGM    -   24-   |   RTN
3. RUN SST          |   -5.00 W/PRGM     00 00-   |   At top of memory


[Continuation 1]
4. RUN SST SST      |   -5.00 W/PRGM        11-   |   Executes LBL, A (no action)
5. RUN SST SST      |   -0.20 W/PRGM        04-   |   Executes g,4 (= g 1/x)
6. RUN SST          |    4.00 W/PRGM        24-   |   RTN	

[Continuation 2]
4. RUN SST SST SST  |   -5.00 W/PRGM        35-   |   Executes LBL, A, g (no action)
5. RUN SST          |    4.   W/PRGM        04-   |   Executes 4 (g-shift cleared)
6. RUN SST          |    4.00 W/PRGM        24-   |   RTN	

[Continuation 3]
4. RUN SST          |   -5.00 W/PRGM        23-   |   LBL (executes as NOP)	
5. RUN SST          |   -0.20 W/PRGM        11-   |   Executes A (entire LBL A subroutine)
6. RUN SST          |   -0.20 W/PRGM        35-   |   g (step 03)	
7. RUN SST          |    4.   W/PRGM        04-   |   Number key 4 (g-shift cleared)
8. RUN SST          |    4.00 W/PRGM        24-   |   RTN