Commodore 797

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Calculators: Handheld: Commodore 797


	Size (approx):	67mm (max) x 157mm x 25mm (max) (w,h,d) Weight 88g excluding 134g including batteries.
	Power:	9.0V DC, 1 x PP3 size battery. It accepts adapter (DC-520R or 505, 506, 507) through a socket on the left hand side in the middle.
	Case:	Beige matt plastic two-piece case with matt black keyboard surround. Typical bright Commodore keys that are wobbly and squishy but positive. A heavily inset flat red plastic display filter gives a good clean display though of limited angle of view. Silver painted raised logos have survived rather well above and below the display.
	Display:	8 digit red bubble-lens LED with a ninth digit for error, memory and negative signs.
	Features:	Standard four functions, register exchange percentages and four function memory
	Age:	1976
	Manufacturer:	Commodore, serial number 46830. 201092-04 made in Hong Kong.
	Comments:	Taller and slimmer than most Commodores of this era, the large upper area accommodates the battery but the longer keyboard is needed for the larger sized keys. Built with the minimum of components to keep the costs as low as possible in a aggressive market of the time. The logic is very sound with good recovery and only let down by the lack of a constant function.

Components:	1 x cpu: Commodore 3D-98MT 3476 (week 34 of 1976) 22 pin DIL 1 x 9 digit single unit bubble lens LED display
Boards:	The main CPU board (Ref: 21461-1) is also the keyboard support and is held onto the front with 9 screws.
Construction:	Remove the single screw from within the battery compartment. Then use a small screwdriver to push the lugs to the outside in the lower lug recesses. The back then lifts off by hinging off the two small top lugs.

Logic comments:	(C/CE) is used once to cancel the last number entered and a second time to clear the whole calculator.
	There is no constant on any function
	Input overflow is suppressed, inputting an ninth digit is ignored
	Negative numbers are shown with a "-" in the immediate left hand digit travelling into the far left (ninth) digit to allow full eight digit negative numbers.
	The (MR) key recalls the memory, the (MT) key totals the memory and clears it.
	Memory store is indicated by the far left (ninth) decimal point
	It is possible to store an overflow in the memory and later recover it by continual division by 10
	Divide by zero shows "E00000000" (no decimal point) and is recoverable by dividing by one
	Overflow shows the result with "E" (negative or positive) in the far left (ninth) digit and is recoverable by continual division by 10.
	(EX) is used to exchange the display contents with the register
	The (%) button divides by 100 (and can be used to recover overflows)