HP-41

The 1979 HP-41 series programmable calculator, produced until 1990, was famously used in the Space Shuttle missions. It featured an LCD alphanumeric display and was powered by a processor initially called "Coconut" (or 1LE3 CPU), later more broadly known as the Nut CPU. The calculator included RAM, ROM, and I/O capabilities, utilizing the interpreted programming language FOCAL ("Forty One Calculator Language"). Both the operating system and the interpreter were stored in ROM, programmed using the Coconut processor's assembly language, also called MCODE (or "M-Code"). A later upgrade, the NEWT Microprocessor, further enhanced its capabilities.

What truly sets this calculator apart are its hardware expansion slots. These allowed users to significantly expand its functionality by adding various components such as memory modules, printer interfaces, card readers, barcode wands, and specialized application modules. This innovative design was a clear precursor to the expansion slots found in modern computers. The HP-41 also famously utilized Reverse Polish Notation (RPN) for its input logic.

While it naturally lacked the processing power and versatility of modern portable computing devices, the HP-41's design philosophy—rooted in portability and user customization—profoundly influenced the development of more advanced mobile computing equipment. The HP-41C, for instance, was a popular model in the series, recognized for its "Continuous Memory" feature.

• HP-41C, at wikipedia.org .
• HP-41 Library, at hp1.org .
• A_programmers_handbook_v.2.07, by Poul Kaarup, 2015.
• CPU Detailed Description, by Hewlett-Packard, 1981.
• Schematic, Hewlett-Packard, 2000.
• ROM listing
  • http://www.hp41.org/LibView.cfm?Command=View&ItemID=1064
  • http://www.hp41.org/LibView.cfm?Command=View&ItemID=304
• Monte Dalrymple's "Inside the NUT CPU" - provides an in-depth look at the Nut CPU, which is the central processing unit of the HP-41 calculator series. It delves into the architecture, design, and functionality of the CPU.
• Doug Wilder´s "QuinTable.pdf" - HP-41 microcode table, the low-level instructions that control the operations of the HP-41 calculator series.
• David's assembler manual - comprehensive guide that provides detailed instructions on how to use the assembler software for programming the HP-41.
• Monte Dalrymple's "NEWT Microprocessor Technical Manual" - the NEWT (Nut, Expanded, With Turbo) CPU is an upgraded version of the Hewlett-Packard Nut microprocessor, which was employed in a number of HP calculators, including the HP-41 series.
• Ken Emery's "HP-41 MCODE For Beginners" - MCODE is the internal machine code used by the HP-41, one level below the set of "user code" instructions that users and programmers are accustomed to dealing with. Some user code instructions like CLX are implemented by the HP-41 in just a few MCODE instructions; other user code instructions like TAN consist of hundreds of MCODE operations.
• HP-41 IC Specifications
  • https://literature.hpcalc.org/items/865
  • https://literature.hpcalc.org/items/866
• Rich Hawkes' "Nonpareil RPN HP-41 Calculator Build" - DIY hardware version of the HP-41.
• go41c calculator - Android App.
• Online HP-41C OWNER’S HANDBOOK AND PROGRAMMING GUIDE.

_{Last edited: 2025-06-07 21:45:43}