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Hewlett-Packard HP-41C

Date of introduction:  July 1, 1979 Display technology:  LCD 14-segment
New price:  $295.00 (SRP 1979) Display size:  10 + 2 
Size:  5.7" x 3.1" x 1.20"
 144 x 79 x 31 mm3
   
Weight:  5.8 ounces, 165 grams Serial No:  2103A03482
Batteries:  4*N Alkaline Date of manufacture:  wk 03 year 1981
AC-Adapter:   Origin of manufacture:  United States
Precision:  10 Integrated circuits:  
Memories:  0-63    
Program steps:  441-0 Courtesy of:  Ken H. Meine

The HP-41C could be called a small revolution in the pocket. Following the path of Programmable Pocket Calculators like the HP-67 or TI-59 it overcame the limitations of their simple men-machine interface possible with a numerical keypad and a 7-segment display. The HP-41C added alphanumeric capabilities to both the display and keyboard using 14-segments and an ALPHA-key. In addition the memory capacity was enhanced and uses non-volatile integrated circuits (RAM) like the TI-58C.

A total of 4 slots allowed further expansion of either RAM capacity, pre-programmed ROM-modules or peripheral devices like a card reader or printer modules. A clever mechanism allows for snap-in keyboard overlays to further customize the HP-41C.

The HP-41C still uses the Reverse Polish Notation with the [ENTER] key instead the usual [=] key.

Understanding the game of cat and mouse with Hewlett Packard, Texas Instruments initiated already in Summer 1977 the "Project X" with clear objectives in mind:

To provide upgrade leadership product to replace TI-59
Expand concepts of problem solving via calculator device
Incorporate:
   - State-of-the-art Technologies
   - System Design
   - System Expansion
To simplify ease of use and provide market expansion among professionals and end users:
   - Technical Professionals
   - Non-Technical Professionals

The ambitious requirements for "Project X" were finalized in January 1978:

Equation Operating System (EOS)
   - Equation can be entered without execution
   - Display will scroll when full
   - Equation can be edited (Backstep, Insert, Delete)
   - Equation is saved to be executed or repeated with new data
16 Character 5*7 dot matrix display
   - Full alphanumeric display
   - Equation trace and prompting in the display
More flexible user memory
   - Basic memory is 1,000 program steps or 125 data registers with partitioning by the user
   - Solid State Software approach (CROM) has been expanded to include Drop-in RAM (CRAM).
   - CROMs and CRAMs are interchangeable and two slots are available on the calculator
   - Basic memory can be expanded to 3,000 steps of 375 data registers
   - CROMs will be 15k program steps, up to 99 programs per CROM, up to 10k steps per program

Hewlett Packard took Texas Instruments by surprise when they introduced with the HP-41C already in July 1979 a Programmable Pocket Calculator almost matching the requirements of their "Project X" - planned for an introduction earliest in Spring 1981! History tells us that TI announced the TI Programmable 88 with CRAM/CROM modules and its peripherals on May 26, 1982 ahead of the Summer Consumer Electronic Show CES, knowing that the polysilicon gate CMOS process used with the TP0485 microcontroller was finally in good shape but the design of the chip still needed some fixes requiring one or two additional manufacturing runs. Consequently the small printed read: "Availability expected late 4th Quarter" and TI cancelled the TI-88 on September 10, 1982 with only a few devices manufactured.

Learn more about the demanding "Project X" initiated already in Summer 1977 and leading not only to the (failed) TI Programmable 88, but the TI-66 PROGRAMMABLE, failed TI-76 PROGRAMMABLE, Compact Computer CC 40, (failed Compact Computer CC 70) and last but not least the successful TI-74 BASICALC and TI-95 PROCALC.

It took some time before Texas Instruments took the leadership again with the introduction of their first Graphing calculator TI-81 in 1990.

For Hewlett Packard the HP-41C was a massive success and its upgrade successors HP-41CV with "V" being the Roman Numeral for 5-times the memory capacity and HP-41CX with CV specs plus Time module, were manufactured till November 1990. Even today, more than 40 years after its introduction, the HP-41C family of keystroke Programmable Calculators receives an incredible support from its die-hard community.

Dismantling the featured HP-41C with Date code 2103A manufactured in January 1981 by Hewlett Packard in the United States reveals a perfect engineered printed circuit board (PCB) centered around a CPU (Central Processing Unit) with 56-bit Registers and a 16-bit Program Counter and powered by 4 N-size batteries.

The microprogramming of the CPU is realized with 3 Instruction-ROMs (Read-only Memories) of 40k Bit capacity, each for a combined 12k*10-bit program size and communicating with a serial data bus. User program and user data, both numeric or alphanumeric, are stored in 5 RAMs (Random-access Memory) of 896 Bits capacity, each for a combined 80 registers with 64 registers available for the user. The 12-character LC-Display with 14 digit segments, 3 punctuation marks and 1 annunciator space is organized in a 72 Segments * 3 Commons matrix and uses two display drivers bonded in Chip-on-Board (COB) technology directly to the PCB and covered with a small epoxy blob. An integrated DC/DC converter generates not only the various voltage supplies for the main electronics but three different, temperature-compensated voltage levels for the LC-Display.


 

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If you have additions to the above article please email: joerg@datamath.org.

Joerg Woerner, Januiary 23, 2021. No reprints without written permission.