Casio Mini CM-602

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Calculators: Handheld: Casio Mini (aka CM-602)

	Size (approx):	153mm x 81mm x 37mm (w,h,d) Weight 240g excluding batteries
	Power:	6V DC, 4 x AA size batteries. It accepts an adapter (AD-4145, 500mW) through a socket on the top side at the far left. Quoted lifetime of alkaline batteries is 10 to 12 hours. The battery compartment has a red ribbon pull to aid removal.
	Case:	Horizontal format two-piece case in black textured plastic. The top and bottom edge have wrap around metal plates that give it a very solid feel. The slightly inset and flat neutral display filter has a printed white border. Below sits a black printed metallic sticker in its own recess. The large, long travel hollow sounding keys work well. The rear information sticker is upside-down. There is a metal post on the right side near the top for the black plastic carry strap.
	.Display:	6 digit blue VFD, with no seventh digit but a display shift key to display up to 12 digits, small zero notation (see below).
	Features:	4 function calculator with display shift for 12 digit precision. Switched two digit financial input mode.
	Age:	1973
	Manufacturer:	Casio Computer Company Ltd. Made in Japan, serial No. 1093964 (on battery cover) and 9117958 (inside battery compartment).
	Comments:	One of a range of early, solidly built horizontal calculators by Casio. This one is probably the most basic with six digits and the early and short-lived shift key. Logic is pretty shaky with no recovery, dodgy minus sign and rubbish display. Not difficult to guess by the very large component count and early date codes this is one of the first Casio pocket-sized calculators (it is in fact the second after the CM-601). The original case is a side-bottom-side zipper with no gap for the carry strap to poke through. It is embossed with a large Casio logo on the front and Made in Japan on the rear.

Components:	On the CPU board: 1 x cpu: Hitachi HD32154P 3L 4 (4th week of November 1973), 28 pin DIL, 0.6" width 1 x IC: Toshiba T3144 3-J (September 1973), 16 pin DIL, 0.3" width 1 x 6 digit VFD; single tube round face, NEC LD8088, Tube No. 716 (the first digit may be a Kanji character) 2 x diodes 1 x capacitor 4 x resistors 3 x resistor arrays On the power/display driver board: 6 x transistors 7 x diodes 15 x capacitors 12 x resistors 1 x transformer
Boards:	The main cpu board (6D-1 B) holds the keyboard assembly. Underneath sits a power board (Fuji MDP-0606 A60447) is of nearly the same size connected via 12 strong wires.
Construction:	Remove the two screws, one at each side end, and the back lifts off easily. Or the front if you like as the whole calculator assembly floats free.

Logic comments:	The (C) button is used to clear last entry of a number and a second press (or the sequence (=)(C) ) clears the whole calculator.
	Overflow on number input is suppressed, typing in a seven digit number ignores the seventh digit.
	An overflow error is flagged with all zeros being displayed and is not recoverable
	Divide by zero error is ignored and calculation can continue with the zero result.
	There is no constant on any function
	Negative numbers are shown with a "-" in the digit to the immediate left of the number so you are limited to five digit negative numbers. My example does not show this sign ever. As it does not show an error - but a correct six digit number with no sign, I am beginning to doubt it ever did!
	The shift key (>), called the "Full Register Viewing Key" by Casio, shows you the least significant six digits for the product or quotient of your calculation. i.e. it only works on multiply and divide.
	A switch selects two digit mode which is like a financial input; keying in (1)(2)(3) result in the input of "1.23"

	Note the unusual way that zero is represented - by only using the lower half of the digit (representative image).
	With the front panel off you can clearly see the main cpu board. The power board sits underneath separated by a sticky piece of stiff card. Most of the components are on the second board which is nearly the same size. Notice the VFD tube sits in its own cut-out to try and reduce the thickness. Compare in a window with the Casio CM-603A.
	The manual measures 148mm by 106mm and is 24 printed pages in one colour black only. The large format allows plenty of space for detailed specification, keyboard definitions and a large number of examples. This example is in English only and is printed in Japan. There is even a section entitled "Practical Examples" that has instructions on such things as Seven Bridge Game, Approximate Calculations, Disregarding the Zeros and Disregarding the Decimal Point.