Commodore P50

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Calculators: Handheld: Commodore P50

		Size (approx):	80mm (max) x 150mm x 31mm (max) (w,h,d) Weight 124g excluding batteries
		Power:	9V DC, 1xPP3 size battery. Also accepts an adaptor (DC-505, 707, 708 or 709, 9V centre positive, though 6V is enough) through a socket on the top side in the middle. There is a power-save display switch off after just over a minute.
		Case:	Two-piece stippled brown plastic case with silver painted trim and raised logo (worn off on this example). The keys in chocolate brown, light brown, beige and white are an unusual departure from the normal commodore primary colours. They are engraved and fill-painted in white or dark brown and have a loose with soft click action. The red plastic display filter is flat, heavily tilted and deeply inset into the top of the case.
		Display:	12 digit red LED with bubble lens: 8+2 scientific mode with two extra digits for negative and error indication.
		Features:	Standard four functions, square root, reciprocal, pi, squares, factorial, sign change, register exchange, integer, five function memory, trig and transcendental functions, DRG, programmable.
		Age:	c1975
		Manufacturer:	Commodore Electronic Calculators. Made in Hong Kong. Serial No. 63947. 201450-04.
		Comments:	Unusual departure from the normal black Commodore calculators. One of only two that they ever did and, of course, made redundant as soon as computers became affordable. The logic is sound but let down by the lack of constants, poor recover and power 99 bug. The original cover is soft black plastic with a flip over top flap and front popper closing. It has Mad in Japan embossed on the front and the Commodore logo on the back.

Components:	1 x CPU: MOS MPS7561 0083778, 28 pin DIL, 0.6" width 1 x 12 digit red LED display unit with individual bubble lenses
Boards:	One main board (aw636a) which serves as the cpu board and keyboard assembly. It is held in place by four plastic guides and eight screws.
Construction:	Remove the two screws from the back and the back section will lift off easily, hinging from the bottom.

Logic comments:	(C/CE) is used once to cancel the last number entered and a second time to clear the whole calculator
	Input overflow is suppressed, inputting an ninth digit is ignored
	There is no constant on any functions - I guess you have to write a programme!
	Negative numbers are shown with a "-" in the far left (twelfth) digit thereby allowing full eight digit negative numbers
	The change sign can be used in mid number entry, even for the exponent
	Overflow normally just shows "E" in the far left (twelfth) digit and is not recoverable
	Divide by zero just shows "E" in the far left (twelfth) digit and is not recoverable
	Negative square roots are not allowed and result in an overflow which is not recoverable
	Use the memory with (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 indication of memory store - you have to remember it
	I do not have a manual with my example but the programmable keys are learn, (Lrn), Run/Stop (R/S), single step (SSTP), goto label (GOTO) and I think the (SKZ) (SKN) and (SKP) keys are skip branch commands
	After just over a minute the power save function switch off the display except for the fourth digit (or sometimes other) decimal point. This function does not work if you haven't pressed the equals key.,
	It suffers and overflow bug: key in (9)(EE)(9)(9)(X)(9)(EE)(9)(9)(=) to give you "0.81"
	Display in scientific mode is eight mantissa and two exponent with two extra digits for negative indication. Internal precision appears to be 11 digits: i.e. (pi)(-)(3)(.)(1)(4)(1)(5)(9)(2)(7)(=) "-4.46 x 10^-8"