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An HP-41CV. The wide ENTERkey (left in the middle of the keypad) and the lack of the equal key (=) are characteristic of the UPN input logic used by the operators

The HP-41C and the successor models HP-41CV and CX were programmable pocket calculators from Hewlett-Packard . The first model of the 41 series came on the market in 1979, and production of the series ended in 1990. In spite of their relatively high prices (from DM 750 , according to today's purchasing power approx. 870 euros ), the computers quickly developed into an important tool for scientists, engineers and students. In addition to extensive programming and expansion options, they were the first devices of this kind to offer an alphanumeric display with energy-saving liquid crystals compared to the LED displays customary at the time .

The pocket calculators were - unusual for devices then and now - very versatile and extensively expandable in a modular way, for example with additional data / program memory , program modules and various peripheral devices such as magnetic card readers, a special reader for barcodes to read in programs and data, printer and cassette drive . To connect the devices, HP developed its own simple bus system , the Hewlett-Packard Interface Loop (HP-IL) with the associated interface, which could be built into the computer using a plug-in module. The later models HP-41CV and HP-41CX were equipped with several times larger memory and additional functions such as a real-time clock (41CX). They were also suitable for automatic control and recording of measured values ​​in smaller laboratory tests using the IEC bus , which was often used. Outwardly, the three models only differed in small details and the model lettering, especially the key assignment and their lettering were identical.

The main distinguishing features compared to the competition from Texas Instruments (especially the TI-59 ) as well as from Casio devices were the great expansion options and the typical HP input using the reverse Polish notation .

Its successors were the functionally very similar HP-42S and the significantly further developed models HP-28 and HP-48 .


HP-41CX with magnetic card reader (the black box above the LC display) and thermal printer
The alphanumeric LC display made it possible for the first time to display letters and special characters on a pocket calculator.

The HP-41C was the first pocket calculator with freely assignable keys . Since the abundance of functions could no longer be sensibly accommodated on the keyboard, a three-stage concept was used:

  • In standard mode, each key has only two functions. A shift or Shiftkey was sufficient for this.
  • Further functions can be called up by entering the function name. To do this, the keyboard is switched to alpha mode, in which every letter of the alphabet plus a few special characters can be entered.
  • In user mode, the user can assign such functions to the individual keys. This allows him to put commands that he needs frequently directly on the keyboard.

In some cases, templates were supplied as keyboard overlays with expansion modules. The alphanumeric capabilities can also be used for programming (in FOCAL ) so that inputs and outputs can be commented on in plain text.

Range of functions

The range of functions in the basic version lagged behind the top models of the previous series. There were no hyperbolic functions or combinatorial commands and no solver, but this was made up for by the expansion modules and the programming options. On the other hand, the character representation enabled a considerable gain in convenience, in order to e.g. B. To add text to inputs and outputs. The stack concept experienced an interesting extension, which now allowed much more flexible manipulations by accessing the stack registers directly (also with memory arithmetic). The option of indexed addressing had also been considerably expanded.

"Synthetic Programming"

By using undocumented command sequences, it was possible to system registry directly access the calculator. This allowed additional properties to be used, which led, for example, to smaller or faster programs, to the display of normally unsupported special characters in the display, to the manipulation of flags in groups or to the use of additional string functions. This procedure, which of course required appropriate caution (e.g. it also allows you to erase the entire memory of the calculator), was called synthetic programming . The term goes back to the title of a book by the American William C. Wickes (developer at HP for pocket calculators), who described some of the functions and introduced possible applications. This type of extended programming led to significant extensions of functionality through numerous pocket calculator clubs that were formed in the 1980s (e.g. CCD - Computer Club Germany with the club magazine Prisma).

Individual development projects went even further and programmed the HP-41 on the level of machine language and developed their own modules or external memory.

Other special features

The models of the HP-41 series belonged to the standard equipment of the American space shuttle vehicles with minor adjustments . They served as pocket calculators for the crew and were u. a. equipped with software to support navigation, to determine radio shadows and to distribute ballast. The time module later offered for the HP-41C / CV and integrated in the HP-41CX contained a real-time clock and was developed at NASA's request. So the computer always had the current time. There was also a stopwatch mode and programs could be started at set times. With the expiry of the HP-41 model series, the computer in the shuttle was replaced by the HP-48 .

By using a Silicon-on-Sapphire process in the production of the CPU, the HP-41 was less sensitive to ionizing radiation than other pocket calculators and therefore predestined for use in space.

The basic model HP-41C appeared only a few months after the HP-34C and was sold parallel to it, but despite its significantly higher price it had fewer functions in the basic configuration. However, it was considerably more versatile, especially due to its alphanumeric capabilities and its expandability. The same was true a few years later for the HP-41CV / CX and the HP-15C .

Technical specifications

  • Classification: Scientific Calculator
  • CPU : CMOS HP SOS Nut (360 kHz clock rate)
  • FPU : none ( BCD arithmetic)
  • ROM : 12 KiB
  • R.A.M.
    • 41C: 445 bytes (expandable to 2237)
    • 41CV / CX: 2237 bytes (convertible into 0 to 319 data registers of 7 bytes each, corresponding to a maximum of 7 program steps, the "320th register" can only be used for program steps because 3 bytes are blocked by the permanent .END. Instruction) (not expandable)
    • 41CX: another 868 bytes (124 registers) extended memory (expandable up to 4200 bytes / 600 registers)
  • Keys: 39 with Shift key
  • Display: Monochrome LC display with 12 characters and fourteen -segment display for alphanumeric output
  • Cassette drive: optional
  • Printer: optionally with direct connection (thermal printer) or other printer via HP-IL
  • Interface Loop ( HP-IL ): optional, thereby significantly expanding the system (measuring devices, floppy disk drive, connection to a PC)
  • Batteries: 4 type "N" ( Lady cells) or power pack with a special adapter
  • Dimensions: length 14.3 cm, width 7.8 cm, height 3.1 cm
  • I / O: 4 slots for various expansion cards such as barcode readers, wired printers and later infrared adapters for external printers, magnetic card readers, additional RAM, software modules, etc.
  • Introduction: July 16, 1979 / discontinuation: January 1, 1990
  • Price at that time:
    • HP-41C: Initially 750  DM , taking into account the change in purchasing power , the comparable euro price would be around 870 euros today, later the price fell, in 1982 it was around 600 DM
    • HP-41CV: List price at the beginning of 1,300 DM (1983), corresponding to a price based on today's purchasing power of approx. 1,240 euros, later the price fell significantly


The slot system allows a large number of peripheral devices to be connected. These include:

Card reader 82104A

The card reader allows programs or data to be written to magnetic cards and read in again, similar to a floppy disk drive. The cards were identical to those of the HP-97 and HP-67 and almost completely compatible with them, the ROM of the reader provided the missing functions. The cards have two strips of 16 registers (112 bytes) each, which can be individually secured against overwriting. The card reader is attached directly to the computer and therefore necessarily occupies port 4.

Time module 82182A

This module (built into the HP-41CX) contains a real-time clock. It can be used as a stopwatch and allows programs to be started automatically at preset times, as well as an acoustic alarm. The module contains special instructions with which the timer crystal can be calibrated very precisely by adding a compensation factor cyclically.

Thermal printer 82143A

The printer can print out up to 24 characters side by side on thermal paper and has limited graphic capabilities (the data must, however, be prepared in a complex manner.) It is supplied from its own power pack; A battery was included for mains-independent operation.

HP barcode scanner for 41C

"Optical Wand" barcode scanner 82153A

The reading pen in the form of a thick ballpoint pen can transfer the HP barcodes ( type 2/5 with proprietary content) to the computer's memory. The data can represent programs (normal or PRIVATE-protected against inspection), data (numbers or letters) or individual keystrokes ( Direct Execution Codes ). One line of barcode consists of up to 16 bytes. The first byte is a checksum for all types, which is calculated from the following 15 bytes according to the formula ([sum of all bytes] MOD 255). The second byte characterizes the type of barcode. Programs can consist of several lines, there it is 16 + [serial number of the line] −1 (programs) or 32 + [serial number of the line] −1 (PRIVATE programs). The third byte indicates whether a function is started in the previous barcode line and bytes are appended in this line (e.g. text). Key commands have a 64 in byte 2.

At the bottom of the pen there is a button that turns on the LED. The barcode reader was powered by the HP-41C. This convenient form of data entry has been widely used.

The extended functions module 82180A

This built-in module in the HP-41CX expands the capabilities of the computer with commands for reallocating the memory, for extended string manipulation, and allows the use of “extended memory”, which can be accessed like a hard disk drive. The module contains 124 registers, which can be expanded up to 600 registers and then, together with the 319 registers of the main memory, cover almost the entire addressable memory space. This expansion is done using the 82181A memory expansion modules (up to 2 possible).

The HP Interface Loop Module HP82160A



Unusually for pocket calculators, the devices still have a fan base 30 years after their production was discontinued. As a result, emulator programs are available for a variety of operating systems, including Windows , Mac OS X , Unix variants, Pocket PC , Palm OS , Apple iOS, and Android . The emulator available for the iPhone contains special functions that can be accessed via iOS system calls (approved by the user), e.g. B. make the location, the altitude above sea level, the compass direction (from the iPhone 3GS) and accelerations of the device (via the built-in 3D accelerometer) available within the HP-41 emulator.


An HP-42S, in the display the stack contents X and Y

When the HP-41 was phased out, Hewlett-Packard launched the next development stage, the HP-42S, alongside the HP-48, a direct successor to the market, which could execute programs from the HP-41 devices with almost the same instruction set. The 42S could control a printer via the built-in IR diode , but there were no other peripheral devices. The computer has a two-line LC matrix display, in the lower half of which menus are displayed that allow access to the extensive function library. This menu navigation allows the keys to be assigned twice. The display also enables a graphic representation, albeit a modest one. The shape of the housing and the supply from three button cells correspond to those of the HP-32S, HP-32SII, HP-20S and others.

Technical specifications of the HP-42S

  • Classification: Scientific Calculator
  • CPU : CMOS "Saturn"
  • FPU : none ( BCD arithmetic)
  • ROM : 64 KiB
  • RAM : 7.2 KiB
  • Keys: 37 with Shift key
  • Display: Monochrome LC matrix display with 131 × 16 pixels (2 lines of 22 characters)
  • Printer: optional (thermal printer via IR)
  • Batteries: 3 × type LR44 or similar
  • Dimensions: length 14.8 cm, width 7.9 cm, height 1.4 cm
  • Introduction: October 31, 1988 / discontinuation: 1995

DM41 / DM41L

DM41L pocket calculator compatible with HP41CX

Based on the sources available for emulators, SwissMicros has reissued an HP41CX-compatible pocket calculator. The small version has the dimensions of a credit card, the large version corresponds to the dimensions and layout of the 10 series. The pocket calculators process the original bytecode, as the CPU is emulated by an ARM processor. The LC matrix display can show all letters of the HP41. The working speed of the computer is adjustable. At maximum speed a DM41 is about 30 times as fast as an original HP41. The power supply of the pocket calculator is done with button cells as in the series 10. The operating system can be updated via a USB connection.

Technical data of the DM41L

  • CPU : LPC1115 ARM (12 MHz or 48 MHz)
  • Display: Monochrome LC matrix display with 132 × 16 pixels (single line)
  • Keys: 39 with shift key and alpha key
  • Battery: 1 × CR2032 (220 mAh)
  • Dimensions: length 5.9 cm, width 8.8 cm, height 0.7 cm

Web links

Individual evidence

  1. ^ William C. Wickes: Synthetic programming on the HP-41C / CV , published in German translation by Heldermann-Verlag Berlin, ISBN 3-88538-800-6 .
  2. ^ A b Archive of the club magazine Prisma: Prisma magazines 1982 to 1992
  3. Best of Prisma, summary of the years 80/81, of the CCD (Computer Club Germany eV), data set in the German National Library
  4. List of popular emulators for the HP-41 , www.hp41.org