Casio 101-MR

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Calculators: Handheld: Casio 101-MR

	Size (approx):	116mm x 154mm x 37.5mm (max) (w,h,d) Weight 312g excluding batteries.
	Power:	6V DC, 4 x AA size batteries. Accepts an adapter/charger (AD-4145 0.57W) through a top side socket on the left.
	Case:	Wide bulky calculator that is made from a rear dark brown (matt and glossy) and front beige glossy plastic case. There is a black plastic display escutcheon that is slightly tilted up. It has a neutral filter with two raised white painted lines framing the digits. Then raised letters sit in their own recess and are painted silver with the company name and model number. A further black plastic panel sits below in its own recess and has white printed text labels for the switches. They well-ordered keys are quite pronounced, long travel and hollow sounding; they still work very well.
	Display:	10 digit blue VFD display with an extra symbol cluster to the far left for negative, memory and constant indicators.
	Features:	Four function with square roots, percentages and four-function memory. Switched rounding and decimal point selection.
	Age:	1974
	Manufacturer:	Casio Computer Co., Ltd. Made in Japan. Serial number 2121442 on battery compartment cover. There is another sticker inside the compartment 29030166.
	Comments:	Big wide calculator that just about fits in the hand but is more likely designed for continuous desktop use. Unusual ten digit model and early "small zero" (see below) display notation. The original case is soft black plastic with top flaps that close with a top popper. It has Casio embossed on the front and Made in Japan on the back. Early logic is a bit shaky with no recovery, negative square roots and archaic RPN input.

Components:	1 x cpu: Hitachi HD32612P 4G 42 (July 1974) 40 pin DIL 0.6" width 1 x IC: Hitachi HD3596 4J 24 (September 1974) 24 pin DIL 0.6" width 1 x single glass tube, round faced 10 digit plus symbol cluster VFD display 1 x transistor 11 x diodes 4 x resistors 4 x resistor arrays 1 x 7 pin SIL package which may be another resistor array 9 x capacitors 1 x transformer module; Fuji MCT 0639 4I-09 (Pat No. 427559)
Boards:	The keyboard assembly (100-E4 B) sits lose on top of the main board and is connected to the main cpu board by 17 stiff wires. The main CPU board (100-1 B) is clip-fixed to the base.
Construction:	Remove the small screw on the top and the front section hinges off easily from the bottom.

Logic comments:	The Clear key (C) is used to clear an input number and the (AC) key to completely reset the calculator
	Overflow on the input of a number is not suppressed, typing in an eleventh digit results in an overflow and is not recoverable
	The selectable constant function on multiply and divide, it not being needed on the (+=) type of keys elsewhere. To switch the constant on you just hit the operator twice; i.e. (5)(X)(X)(3)(+=) shows "15" then (+=) shows "75" etc. A small dot in the far left symbol cluster lights up when constant is selected. To deselect press any operator again.
	The old key system takes a bit of getting used to if you have never seen it. To work out 9-3 key in (9)(+=)(3)(+=)(-=), like Reverse Polish Notation.
	Memory storage is flagged by a small "M" in the far left symbol cluster.
	Negative numbers are flagged by a "-" sign in the far left symbol cluster thereby allowing full ten digit negative numbers.
	Negative square roots are allowed and cause the display digits to ripple away for nearly a second.
	There is a switch to select Floating, round and round down (cut) modes and another to select the number of decimal points from 6,4,3,2,1 and 0.
	A divide by zero shows "E" in the first digit and is not recoverable
	Overflow shows the "E" in the first digit and and is not recoverable

	Note the unusual way that zero is represented - by only using the lower half of the digit.