Mera Elwro 441 Bolek

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Calculators: Handheld: Elwro 441 (aka Bolek)

		Size (approx):	linked not started 68mm x 130mm x 23mm (max) (w x h x d) Weight 86g not including batteries.
		Power:	9.0V DC using 1 x PP3 size battery. It accepts an adapter (DC 9V 0.5W) through a socket on the left hand side just above the display. The on/off switch is on the left hand side in line with the name plate.,
		Case:	Compact model made from a two-piece black matt plastic case. A white printed sticker sits slightly proud in its own recess with the alternative name. The convex (magnifying) red plastic display filter is slightly tilted and gives a clean bright image of the rather narrow view digits. The keyboard surround is printed with blue ellipses and blue and white text. The keys are short travel with a loud click. They are quite loose so the whole thing rattles like a box of matches.
		Display:	8 digit red LED (individual bubble lens) with a ninth digit for memory, function and error indicators but surprisingly not the negative indicator.
		Features:	Basic four function with percentages, square root, reciprocal, squares and five-function memory
		Age:	1978
		Manufacturer:	Mera-Elwro, type Elwro 441, made in Poland, serial number 80 238739
		Comments:	Cheaply made calculator that probably suffers the most unfortunate name ever - in fact it's a load of Boleks! Seriously this is one of three (the others called Jacek and Lolek) with what appears to be Polish/Czech forenames. The logic is not bad with good recovery but let down by seven digit negative numbers and numerous negative zero bugs. Same case as the Radofin 1660 and many other similar ones. Whilst the IC appears to be the same as in the Commodore 9R-25, its functions and artefacts are different.

Components:	1 x cpu: MOS MPS7545 0043978 (date code 1978), 22 pin DIL, 0.6" width black plastic 1x IC: UCY 74548 CEMI, 22 pin DIL, 0.6" width black plastic 1 x 9 digit LED unit with individual bubble lens: Unitra Cemi W1/T 8 x resistors
Boards:	The main cpu board (Elwro 441/C 0731-0280-01) is held over the keyboard assembly by four plastic lugs. There are very long connecting wires to the keyboard assembly which is fixed to the front also by plastic lugs and some guides.
Construction:	One of those difficult ones that is held together with nothing but lugs - if in doubt do not try as damage may result. The easiest way I found was to pop the right hand side lugs by levering out the back section. The inside rear of the case on my example is embossed with "Property of Radofin Model X-4" which I suspect refers to the plastic mould.

Logic comments:	The (C/CE) is used to clear an input number whilst a second press clears the calculator
	Overflow on the input of a number is suppressed: keying in a ninth digit is ignored
	There is automatic constant on all four functions, though the constant is the second entry
	The negative sign is shown in the immediate left hand digit but strangely it does not travel into the ninth digit so it is limited to seven digit negative numbers
	Negative numbers less than one are shown without the leading zero; -0.5 shows as "-.5" rather than "-0.5"
	An overflow shows the result with eight decimal points and “C” (“C-” if negative) in the far left (ninth) digit and is recoverable using (C/CE)
	A divide by zero results in "C.......0." and is not recoverable.
	Negative square roots are not allowed and show the result with all eight decimal points and "C" in the far left (ninth) digit and is recoverable using (C/CE)
	Higher functions are accessed by a two key system, pressing (F) first will case "F" to be displayed in the far left (ninth) digit and is cancelled by pressing (F) again
	Memory store is indicated by the decimal point of the far left (ninth) digit
	Memory overflow is flagged, recoverable and retains the original number
	It suffers the negative zero bug: key in (1)(-)(2)(=) to give "-1", then (+)(1)(=) to give "-0"
	It suffers the divide to negative zero bug: key in (1)(-)(=)(=)(/)(1)(0)(=)(=)(=) etc. until you end up with "-0"