The Commodore GL-996R is an arithmetic calculator that offers 8 digits of precision and operates with algebraic logic. Released in 1975, this calculator is a product of Commodore Japan Limited, with manufacturing taking place in both Japan and the UK. The GL-996R is part of Commodore’s Custom Green Line series, known for its distinctive design and reliable performance.
The calculator features a sturdy, three-piece case constructed from black and white matte plastic. The top front of the case includes an oversized green plastic display filter, which is flush with the case and has a sloping inset section. This design provides a bright and clear image, enhancing the visibility of the display. The Commodore logo, raised and painted silver, along with the words “Custom Green Line,” is prominently featured on the display filter. The calculator’s keys are boldly colored in red, white, and blue, each with its own raised surround. While the keys may feel slightly wobbly and squishy, they function effectively. Below the keyboard, a black printed metallic sticker with the company name sits in its own recess, adding a touch of professionalism to the design.
The Commodore GL-996R is powered by a sealed battery pack, specifically a double AA-sized rechargeable battery pack. The calculator operates on 4.5V DC internal sealed batteries, and an adapter (type No. DC-420B centre positive, 200mA) is used to recharge the built-in Ni-Cd batteries. The charging socket is conveniently located on the right-hand side, just above the midway point.
The display of the GL-996R is an 8-digit green VFD (vacuum fluorescent display) with a ninth digit reserved for negative and error indicators. This ensures that users can see both positive and negative numbers clearly, as well as any error messages that may occur during calculations.
In terms of functionality, the Commodore GL-996R offers standard four-function capabilities, including addition, subtraction, multiplication, and division. It also features percentage calculations and register exchange, making it a versatile tool for various arithmetic tasks.
The calculator’s internal components include a CPU (Commodore GRBP-89 7527), a 9-digit VFD, two transistors, one diode, five capacitors, four resistors, two resistor arrays, one transformer, and the rechargeable battery pack. The main CPU board (PCB 200432 Art 200433 Rev B) sits on top of the keyboard assembly and is held in place with the adapter socket. The two are joined by a long 14-way ribbon cable, and the keyboard assembly is fixed to the front with ten screws.
Disassembling the Commodore GL-996R can be challenging due to the tight internal lugs on the sides. Removing the two screws from the back is the first step, but opening the calculator further requires careful maneuvering to avoid damage. A white side lug about halfway between the bottom and the adapter socket needs to be pushed in while prying with a blunt wooden or plastic stick. This process must be repeated on the side and top to fully open the calculator. Reassembling the device is equally tricky.
Logic:
- The (C) key is used on the first press to cancel the last number entered and on the second press to clear the entire calculator.
- Input overflow is suppressed; inputting a ninth digit is ignored.
- Negative numbers display a “-” sign in the immediate left-hand digit, allowing for full eight-digit negative numbers.
- Overflow shows the result and “E” (if positive or negative) in the far left (ninth) digit and is recoverable by continual division by 10 or a multiple.
- Divide by zero shows “E00000000” and is recoverable by dividing by one.
- There is automatic constant on all four functions.
- Percentage just divides by zero so can also be used for overflow recovery.
The Commodore GL-996R is a well-designed calculator with a bold, simple aesthetic that was characteristic of the Custom Green Line series. Its logic is reliable, with good recovery features and no detectable bugs, making it a dependable tool for basic arithmetic calculations.
