The HP-41C series are programmable, expandable, continuous memory handheld RPN calculators made by Hewlett-Packard from 1979 to 1990. The original model, HP-41C, was the first of its kind to offer alphanumeric display capabilities. Later came the HP-41CV and HP-41CX, offering more memory and functionality.

The alphanumeric "revolution"

thumb|The HP-41C's alphanumeric display allowed it to display numbers, characters, and symbols.

thumb|upright=0.9|The HP-41CV had a memory five times larger than that of the first model HP-41C. On the lower, inclined flank of the keys, the alphanumeric characters are printed in blue, which are accessible after pressing the "ALPHA" key top right.

The alphanumeric LCD screen of the HP-41C revolutionized the way a pocket calculator could be used, providing user friendliness (for its time) and expandability (keyboard-unassigned functions could be spelled out alphabetically). By using an alphanumeric display, the calculator could tell the user what was going on: it could display error messages, such as showing ("<samp>DATA ERROR</samp>") upon attempting to divide by zero instead of simply displaying a blinking zero; it could also specifically prompt the user for arguments ("<samp>ENTER RADIUS</samp>") instead of just displaying a question mark.

Earlier calculators needed a key, or key combination, for every available function. The HP-67 had three shift keys (gold "f", blue "g" and black "h" prefix keys); the competing Texas Instruments calculators had two ( and ) and close to 50 keys (the TI-59 had 45). Hewlett-Packard were constrained by their one byte only instruction format. The more flexible storage format for programs in the TI-59 allowed combining more keys into one instruction. The longest instruction required eleven keypresses, re-using the shift keys four times. The TI-59 also made use of the key followed by two digits to access another 40 different functions, but the user had to remember the codes for them. Clearly, a more convenient and flexible method of executing the calculator's instructions was needed. The HP-41C had a relatively small keyboard, and only one shift key, but provided hundreds of functions. Every function that was not assigned to a key could be invoked through the key (pronounced EXEQTE&nbsp;&mdash; "execute") and spelled out in full, e.g. FACT for the factorial function.

The calculator had a special user mode where the user could assign any function to any key if the default assignments provided by HP were not suited to a specific application. For this mode, the HP-41C came with blank keyboard templates; i.e. plastic covers with holes for the keys, so the user could annotate customized keys. Hewlett-Packard even sold a version of the calculator where hardly any keys had function names printed on them, meant for users who would be using the HP-41C for custom calculations only (thus not needing the standard key layout at all); this version of the calculator was colloquially known, within HP's Corvallis calculator team, as a "Blanknut" (because the development code name for the HP-41C's processor was known as the "coconut"). The HP41CL is a ground up redesign of the components found on the HP-41 CPU board, including the CPU, which is implemented on an FPGA and coded in Verilog RTL. The HP41CL upgrade board is made as a drop-in replacement for the HP-41 series CPU board, assuming that one has an HP-41 that has a compatible CPU board connector and a separate CPU board as well. The upgrade comes with an over 600 register extended memory and over 320 plug-in module images. Furthermore, an optional RS-232 full-duplex serial connector (with a 2.5mm stereo jack physical interface) is available, if one has a free module slot.

Emulators

thumb|upright=0.8|An emulation [[Mobile Application|app for the HP-41CX running on Apple iOS. Additionally, the simulated output of the thermal printer can be displayed.]]

Unusually for pocket calculators, the devices still have a fan base more than 30 years after their production was discontinued in 1989. As a result, emulator programs are available for a variety of operating systems, including Windows, Mac OS, Unix variants, Pocket PC, Palm OS, Apple iOS and Android.

Images

<gallery widths=180>

File:0934 - HP41CX.jpg|Alphanumeric display of an HP-41CX

File:Interface loop module HP-IL for connecting HP-41 calculators with peripheral devices.jpg|HP-IL interface module

File:Thermal printer HP82162A and IL-Loop and HP41CX.jpg|HP82162A thermal printer (with HP-IL connection)

File:Digital cassette drive HP82161A for HP-41 calculator series.jpg|HP82161A cassette drive with storage medium (with HP-IL connection)

File:HP-41CX connected to thermal printer and digital cassette drive via HP-IL interface loop.jpg|Interface loop with thermal printer HP82162A (front left), a cassette drive HP82161A (back left) and an HP-41CX

File:Rear connectors of video interface HP82163B for HP-41 calculators w. TV-UHF and AV output.jpg|HP 82163B&nbsp;- 32 columns video interface for HP-IL

File:0978 - HP41CX Expansion Slots.jpg|Extension slots of an HP-41CX

File:0943 - HP82242A IR-Interface.jpg|HP82242A IR-interface (to a thermal printer)

File:Card reader-writer 82104A for calculator HP41C.jpg|HP 82104A&nbsp;- card reader/writer for HP-41C

File:0986 - HP41CX X Memory HP82181A.jpg|X Memory module HP82181A (memory extension)

File:0992 - HP41CX Stat I.jpg|Statistics module

File:1028 - HP82106A.jpg|HP 82106A memory module for HP-41C

File:1022 - HP82120A.jpg|HP 82120A battery pack for the HP-41CX with damaged NiCd cells (original)

File:0995 - HP41CX Bat Pack.jpg|HP 82120A battery pack for the HP-41CX (the original NiCd cells were replaced by NiMH cells)

</gallery>

See also

  • FOCAL character set
  • HP calculators
  • NOMAS (support)

References

Further reading

thumb|right|Developer view of the 14 segment LCD Code of the HP41CX Calculator emulation

  • SwissMicros DM41X and DM41L
  • HP-41CL a modded version with 50x speed 120 module integrated
  • The Museum of HP Calculators' article on the HP-41 series
  • hp41.org &ndash; A website (and domain) dedicated to the HP-41
  • HP41 Forum
  • i41CX+ HP-41CX Emulator for the iPhone and iPod touch
  • a41CV An HP41CV simulator for the Android platform
  • HP-41C, HP-41CV and HP-41CX on MyCalcDB (bilingual) (database about 1970s and 1980s pocket calculators)
  • Page of an HP-41CX user with photos, documents for download, printer, card reader...
  • C++ (linux, QT) Source-code project. Simulator HP41CX in a nearly natural look. Based on nsim-0.61 NUT Core by Eric Smith.
  • clonix41.org&nbsp;- A website (and domain) with some interesting enhancements for the HP-41