Hewlett-Packard HP-75C

Date of introduction:  September 15, 1982 Display technology:  LCD dot matrix
New price:  $995.00 (SRP 1982) Display size:  32 (12 + 2)
Size:  5.1" x 10.1" x 1.3"
 129 x 257 x 33 mm3
Weight:  23.6 ounces, 668 grams Serial No:  2242A00426
Batteries:  3*AA NiCd Date of manufacture:  wk 42 year 1982
AC-Adapter:  HP-82059 Origin of manufacture:  United States
Precision:  12 Integrated circuits:  
Memories:  16kB RAM, 48kB ROM    
Program steps:   Courtesy of:  Joerg Woerner

We assume that Hewlett Packard was as impressed as their main competitor Texas Instruments, when Matsushita announced in September 1980 in Japan one of the World's first Hand-Held Computers and named it accordingly HHC.

Hewlett Packard introduced already in July 1979 with the HP-41C an innovative Programmable Pocket Calculator with an alphanumeric LC-Display to overcome the limitations of the first generation products like HP-67 and TI-59, but is was still using simple keystroke programming. While Sharp's PC-1211 and Casio's FX-702P replaced keystroke programmability with a much more powerful BASIC interpreter, introduced the Panasonic HHC System so-called plug-in ROMs (Read-only Memory) not only for user applications but for programming language support, too. Users could chose in 1981 between BASIC or FORTH and develop their target applications accordingly.

The HP-75C introduced about two years after the Panasonic HHC and improved every aspect of the Panasonic RL-H1400 and its stable mates, but lacked the multi-language support:

Introduction Product MSRP Form Display Operation,
Program Size
Data Size
Archive Ports Battery Operating
Year Mth Company Model Size Techn. Logic PGM Mode Steps M Memories B
1980 9 Panasonic RL-H1400 $500 (1981) L 26 Dot M. LCD AOS BASIC
4.0k Bytes RAM Y External 3 5*AA NiCd 100-1,000h
1982 9 Hewlett Packard HP-75C $995 (1982) L 32 Dot M. LCD AOS BASIC 16.0k Bytes RAM Y Mag. Card 4 3*AA NiCd 100-1,000h

Like the Panasonic HHC the HP-75C was the center of a Portable Computer System and it connected through the innovative HP-IL (Hewlett Packard Interface Loop) to a maximum of 30 devices including printers, tape recorders, floppy disc drives, and more. The four integrated ports accepted either up to three additional ROMs or one additional RAM module. 

The HP-75D added in 1984 a port for a barcode reader to the HP-75C but it was much less popular than the smaller and more affordable HP-71B introduced in the same year.

Dismantling the featured HP-75C with Date code 2242A manufactured in October 1982 by Hewlett Packard in the United States reveals a sandwich construction with two large printed circuit boards (PCBs) centered around an HP-proprietary 8-bit CPU (Central Processing Unit) on the Main-PCB supported with various ROM (Read-only Memory) and Display Driver chips. The second PCB is configured with 8 TC5516AP chips with a capacity of 8n Bytes, each and manufactured by Toshiba in Japan. The HP-75C is powered by 3 AA-size rechargeable batteries and a DC/DC converter provides the various voltages for the main electronics and the display.


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Joerg Woerner, December 31, 2020. No reprints without written permission.