The Commodore 899A is a handheld calculator released between 1976 and 1977. Notable for its robust design and practical features, this model represents a slice of mid-1970s computational technology with a range of standard and more advanced functions. The 899A is both compact and lightweight, making it a convenient option in its time for both personal and professional calculations. Here’s an in-depth look at its design, features, and operational logic.
Specifications and Design
- Dimensions and Weight: The Commodore 899A measures approximately 75mm wide, 147mm high, and 25mm deep, weighing 110 grams without batteries.
- Power Supply: It operates on a 9V DC power supply using a PP3 battery but also supports adapters (DC-620 or 505, 506, or 507) with a center-positive setup through a socket on the top left side.
- Body and Aesthetic: The calculator has a cream-colored matte plastic casing with a matte black keyboard surround. The keyboard features Commodore’s signature colorful keys, which, though soft to the touch, provide a tactile user experience. Its red plastic display filter enhances display clarity, albeit with a limited viewing angle. The Commodore logo is embossed at the top, giving it a professional look.
- Display: The 899A features an 8-digit red bubble-lens LED display, with a ninth digit to indicate errors, memory, and negative signs.
Functional Capabilities
- Basic Operations: It performs the four basic arithmetic functions, including addition, subtraction, multiplication, and division.
- Additional Features: Advanced functions include percentages, reciprocal calculations, squares, square roots, changing signs, and register exchange. It also includes constants for calculations with π (pi) and offers a five-function memory, which includes memory register exchange.
Construction and Components
- Internal Components: The Commodore 3D32C ML980 CPU is housed within the calculator and connected to a 9-digit single-unit bubble lens LED display.
- Circuit Boards: The keyboard board, made in Japan, attaches securely to the front casing using ten screws and connects to the main CPU board via a 12-way ribbon cable.
- Assembly: Disassembly involves removing two rear screws and disengaging lugs to lift off the back cover.
Logic and Operation
- (C/CE) button clears the last entry on the first press and clears the entire calculator on the second press.
- Automatic constant available for all four basic functions.
- Suppressed overflow: If a ninth digit is inputted, it is ignored.
- Negative numbers display with a “-” on the leftmost digit, allowing full eight-digit negative values.
- Divide by zero shows “0” and “E” on the leftmost digit, which is recoverable by pressing (C/CE).
- Overflow displays with “E” on the leftmost digit for positive or negative values and is recoverable using (C/CE).
- Change sign function can be used during mid-number entry.
- Negative square roots are permitted, resulting in a negative number.
- Memory indicator: An upper “n” appears on the leftmost digit.
- Memory operations: (MT) recalls and clears memory; (X-M) exchanges memory with the current register.
- Memory overflow stores the shifted result with an error.
- (X-Y) exchanges the display value with the register.
The Commodore 899A delivers a mix of essential and advanced functionalities in a durable, vintage design. Its thoughtful engineering, solid logic handling, and user-friendly interface make it a distinctive calculator from an era when computational devices were gaining popularity in both personal and professional spheres.
