Decimo Handy

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Calculators: Handheld: Decimo Handy (aka 508A)

		Size (approx):	72mm x 107mm x 21mm(max) (w,h,d) Weight 84g excluding batteries
		Power:	9V DC, 1 x PP3 size battery. It accepts an adaptor (undefined) through a socket on the top side to the far left.
		Case:	Compact palm-sized one-piece white matt plastic case. There is a third black gloss/matt section which makes up the top, front and keyboard surround. A raised, ridged area has a raised lettered panel with the brand and model name which was originally painted silver. The display filter is tilted red plastic with a linear convex shape for extra magnification. This gives a large bright display with a limited angle of view. They keys are short travel with a positive click and individual escutcheons.
		Display:	8 digit red LED with individual bubble lens and no ninth digit (there is physically a ninth digit but it's never used)
		Features:	Standard four functions with percentages
		Age:	1976
		Manufacturer:	Made in Singapore with a serial number 61009222
		Comments:	Palm-sized compact calculator with an attractive layout. There was at least one other model in this range the Handy M. The logic is weak - let down by inconsistent recovery, seven digit negative numbers and divide to minus zero bug. The original case is soft black plastic with square edges, an open top and half-moon cut-outs either side.

Components:	1x cpu: (square spiral logo) C683 7610 (date code week 10 of 1976), 28 pin DIL, 0.6" width black plastic 1 x IC: National Semiconductor DS8871N 617 (date code week 17 of 1976), 18 pin DIL, 0.3" width black plastic 1 x 9 digit red LED display unit with bubble lens: National Semiconductor A1185B 540 9 x resistors 1 x capacitor
Boards:	The Keyboard assembly (K108 AW 145268 Rev A) sits on top of the main cpu board (SPL-0045) and is connected with 15 strong wires.
Construction:	Remove the small screw visible from the back. The black section can then be slid up and the whole inside assembly, including keyboard will slide up too.

Logic comments:	(C) is used to cancel the last number entered and a second press will clear the whole calculator
	Input overflow is suppressed, keying in a ninth digit is ignored
	Negative numbers are represented by a “-“ in the immediate left hand digit but as there is no ninth digit to travel into you are limited to seven digit negative numbers
	There is automatic constant on all four functions
	Overflow shows the result with all decimal points alight and is recoverable using (C)
	Divide by zero shows ".......0." and is not recoverable
	It suffers the divide to minus zero bug: key in (-)(1)(/)(1)(0)(=) to give "-0.1" then continue pressing (=) to eventually get to "-0."