The Citizen 800R calculator, released in 1973, represents a pivotal moment in the evolution of handheld computing devices. This sturdy machine, equally at home on a desk or in hand, exemplifies the transitional period between the first generation of electronic calculators and the more sophisticated models that would follow.
Measuring 87mm x 150mm x 33mm and weighing 270g with batteries, the 800R strikes a balance between portability and functionality. Its two-tone grey plastic case, adorned with a tilted green display filter and metallic branding sticker, speaks to the aesthetic sensibilities of early 1970s electronics. The large, soft-touch keys provide tactile feedback with a subtle metallic click, enhancing the user experience.
At the heart of the 800R lies a Rockwell 15332PC 7315 CPU, a 42-pin integrated circuit that was cutting-edge for its time. This chip, combined with 18 transistors and various other electronic components, powers the calculator’s operations. The 8-digit green vacuum fluorescent display (VFD) offers clear visibility, supplemented by two red LEDs for overflow and negative value indication.
One of the 800R’s notable features is its power system. It utilizes a 6V rechargeable battery pack consisting of four AA-sized cells, which can be charged via an AC adapter. This dual-power capability made the calculator versatile for both office and mobile use.
The 800R’s functionality, while basic by today’s standards, was comprehensive for its era. It offers the four standard arithmetic operations plus percentage calculations. A unique feature is the three-position switch for selecting between fixed, floating, and financial decimal point modes, catering to different calculation needs.
Logic:
- Uses arithmetic (semi-Reverse Polish Notation) input mode
- (C) key functions as both Clear Entry and Clear All
- Automatic constant function for multiplication and division
- Input overflow is suppressed after 8 digits
- Negative numbers indicated by a red LED
- Overflow results are displayed with a red LED indicator
- Division by zero shows zero with a red LED indicator
- Three decimal point modes: floating, financial, and fixed (4 digits)
- Exhibits the “pseudo fixed decimal bug” common in calculators of its era
The Citizen 800R calculator embodies the rapid technological advancement of the early 1970s. Its combination of a powerful (for the time) CPU, rechargeable battery, and multiple calculation modes made it a versatile tool for both professionals and enthusiasts. While its semi-RPN logic and quirks like the pseudo fixed decimal bug might seem archaic today, they provide a fascinating glimpse into the developmental stages of electronic calculators. The 800R stands as a testament to Citizen’s engineering prowess and the industry’s drive towards more powerful and user-friendly computing devices.
