The Commodore P50 calculator, introduced in 1975, is a scientific calculator that stands out for its unique design and functionality. Manufactured by Commodore Electronic Calculators in Hong Kong, this calculator offers a range of features that cater to both basic and advanced mathematical needs.
The P50 is housed in a two-piece stippled brown plastic case with silver painted trim, featuring a raised Commodore logo. The keys, colored in chocolate brown, light brown, beige, and white, are engraved and fill-painted, providing a tactile experience with a soft click action. This color scheme is a bit different from Commodore’s typical primary colors, giving the calculator a unique look.
The Commodore P50 is powered by a 9V DC battery or an adaptor, with a power-saving feature that turns off the display after just over a minute of inactivity. The red LED display, which is flat and heavily tilted, shows 12 digits, including 8 mantissa and 2 exponent digits in scientific mode. The display also includes two extra digits for negative and error indications, ensuring clarity in calculations.
In terms of functionality, the Commodore P50 calculator offers standard four functions, square root, reciprocal, pi, squares, factorial, sign change, register exchange, integer, five function memory, trig and transcendental functions, DRG, and programmable features. These capabilities make it a versatile calculator compared to competitors.
The calculator’s logic is generally reliable, but it has some limitations. There is a lack of constants, poor error recovery, and a notable power 99 bug. The original cover is made of soft black plastic with a flip-over top flap and front popper closing.
The internal components include a MOS MPS7561 CPU and a 12-digit red LED display unit with individual bubble lenses. The main board serves as both the CPU board and keyboard assembly, held in place by plastic guides and screws. Disassembling the calculator is straightforward, requiring the removal of two screws from the back.
Logic
- The (C/CE) key cancels the last number entered on the first press and clears the entire calculator on the second press.
- Input overflow is suppressed, and entering a ninth digit is ignored.
- There are no constants available for any functions.
- Negative numbers are displayed with a “-” in the far left digit, allowing for full eight-digit negative numbers.
- The change sign key can be used mid-number entry, including for the exponent.
- Overflow and divide by zero errors display an “E” in the far left digit and are not recoverable.
- Negative square roots result in an overflow error that is not recoverable.
- Memory functions include (STO) to store, (RCL) to recall, (M+) to add the current display to memory, (MX) to multiply the current display to memory, and (X<>M) to exchange the display with memory. There is no memory store indication.
- Programmable keys include learn (Lrn), Run/Stop (R/S), single step (SSTP), goto label (GOTO), and skip branch commands (SKZ, SKN, SKP).
- The power-save function turns off the display after just over a minute, except for the fourth digit decimal point, but only if the equals key has been pressed.
- An overflow bug occurs when entering (9)(EE)(9)(9)(X)(9)(EE)(9)(9)(=), resulting in “0.81”.
- The display in scientific mode shows eight mantissa and two exponent digits, with two extra digits for negative indication. The internal precision appears to be 11 digits.
The Commodore P50 is a well-designed calculator with a unique look and a range of mathematical functions. Despite some limitations in its logic and error recovery, it remains a great example of Commodore’s calculator lineup from the mid-1970s.
