HP-42S

The HP-42S RPN Scientific is a programmable RPN Scientific hand held calculator introduced by Hewlett Packard in 1988. It has advanced functions suitable for applications in mathematics, linear algebra, statistical analysis, computer science and others.

HP-42S
The HP-42S
TypeProgrammable scientific
ManufacturerHewlett-Packard
Introduced1988
Discontinued1995
Calculator
Entry modeRPN
Precision12 display digits (15 digits internally),[1] exponent ±499
Display typeLCD dot-matrix
Display size2 lines, 22 characters, 131×16 pixels
CPU
ProcessorSaturn (Lewis)
Programming
Programming language(s)RPN key stroke (fully merged)
Firmware memory64 KB of ROM
Program steps7200
Interfaces
PortsIR (Infrared) printing
Other
Power supply3×1.5V button cell batteries (Panasonic LR44, Duracell PX76A/675A or Energizer 357/303)
Weight6 oz (170 g)
Dimensions148×80×15mm

Overview

Perhaps the HP-42S was to be released as a replacement for the aging HP-41 series as it is designed to be compatible with all programs written for the HP-41. Since it lacked expandability, and lacked any real I/O ability, both key features of the HP-41 series, it was marketed as an HP-15C replacement.

The 42S, however, has a much smaller form factor than the 41, and features many more built-in functions, such as a matrix editor, complex number support, an equation solver, user-defined menus, and basic graphing capabilities (the 42S can draw graphs only by programs). Additionally, it features a two-line dot matrix display, which made stack manipulation easier to understand.

Production of the 42S ended in 1995.[2] As this calculator is regarded amongst the best ever made in terms of quality, key stroke feel, ease of programming, and daily usability for engineers,[3] in the HP calculator community the 42S has become famous for its high prices in online auctions, up to several times its introduction price, which has created a scarcity for utility end users.

Specifications
HP-42S battery compartment and the IR diode
HP42S Calculator Internal Teardown
  • Series: Pioneer
  • Code Name: Davinci
  • Introduction: 1988-10-31
  • 64 KB of ROM
  • 8 KB of RAM
  • Functions: Over 350
  • Expandability: Officially no other than IR printing (32 KB memory upgrade[4] and over-clocking hardware hacks are possible)
  • Peripherals: HP 82240A infrared printer

Features

Programming
Main article: Focal (HP-41)

The HP-42S is keystroke-programmable, meaning that it can remember and later execute sequences of keystrokes to solve particular problems of interest to the user. The HP-42S uses a superset of the HP-41CX FOCAL language.

The HP-42S supports indirect addressing with which it is possible to implement a Universal Turing machine and therefore the programming model of the HP-42S can be considered Turing-complete.

Sample program

This is a sample program which computes the factorial of an input integer number (ignoring the calculator's built-in factorial function). The program consumes 18 bytes. No memory registers are used.

Step Instruction Comment
01 LBLFAC Start of program "FAC"
02 1 1 is put into X, hence the value to be calculated upon (which was initially in X) is lifted (pushed) into stack register Y
03 LBL00 Define label 00
04 RCL×STY Recall stack register Y and multiply with X
05 DSESTY Decrement stack register Y and if not zero ...
06 GTO00 ... go back to label 00
07 END or RTN Returns control (and result in X) to either the user or to a calling program.

Legacy

In May 2017, SwissMicros released pre-production samples of an RPN calculator closely resembling the HP-42S, the DM42. The final product was released on the 9 December 2017. Even though slightly smaller (144×77×13 mm, 170 g) than the original HP-42S (148×80×15 mm, 170 g), the calculator comes with an additional top row of keys for soft menus, a keyboard layout supporting direct alpha character input, a much larger high-contrast display (Sharp low power transflective memory LCD with a resolution of 400×240, protected by Gorilla Glass) showing all four stack levels at once (configurable), ca. 75 KB usable RAM, a beeper, a callable real-time clock as well as an infrared port for HP 82240A/HP 82240B printer support and a USB interface (with Micro-B connector) emulating a FAT16-formatted USB mass storage device for easy program transfer and state backup / transfer as well as for firmware updates. The calculator, which comes in a stainless steel case with matte black physical vapor deposition (PVD) coating, supports keyboard overlays and is based on a modified version of Thomas Okken's GPLed Free42 simulator with Intel's decimal floating-point math library for higher precision (decimal128) running on an STM32L476RG processor (ARM Cortex-M4 core, 128 KB RAM, 1 MB internal flash) with another 8 MB of external QSPI flash (of which ca. 6 MB are available to users). It is powered by a CR2032 coin cell or via USB and clocked dynamically at 24-80 MHz. The DM42 is also the hardware basis for the community-developed WP 43S calculator,[5][6] a successor to the WP 34S.

See also

References
  1. HP-42S RPN Scientific Calculator - Owner's Manual (PDF) (1 ed.). Corvallis, OR, USA: Hewlett-Packard Co. June 1988. p. 3. 00042-90001. Archived (PDF) from the original on 2017-09-17. Retrieved 2017-09-17.
  2. "HP-42S". Museum of HP Calculators. Retrieved 2016-10-27.
  3. http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv020.cgi?read=177373
  4. Hosoda, Takayuki (2007-10-10). "Upgrading the memory of the HP 42S to 32KB". Archived from the original on 2017-09-17. Retrieved 2011-08-12.
  5. Bonin, Walter (2019) [2015]. WP 43S Owner's Manual (PDF). 0.13 (draft ed.). ISBN 978-1-72950098-9. ISBN 1-72950098-6. Retrieved 2019-10-31. (314 pages)
  6. Bonin, Walter (2019) [2015]. WP 43S Reference Manual (PDF). 0.13 (draft ed.). ISBN 978-1-72950106-1. ISBN 1-72950106-0. Retrieved 2019-10-31. (271 pages)

Further reading
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