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Calculators: Desktop: Casio S-1(B)

Size (approx): 132mm x 170mm x 20-42mm  (w,h,d)
Weight 300g excluding batteries


6V DC, 4 x AA size battery, 0.7W.  Also accepts adapter (AD-4145).  Socket on top side on the  far left.
Case: Square design which slightly slopes upward.  The display slopes out at about 45 degrees making it quite prominent and perfect for use on the desk.  It is a two-piece smooth plastic case, grey bottom and white top.  A large tricolour brushed aluminium panel surrounds the keys and switches with reversed-out text for the make and model number.  The bold keys in orange, grey, black and blue are typical squishy, long travel Casio buttons.  They work well to this day.  The neutral display filter gives a bright and high contrast display.
Display: 10 digit blue VFD with an extra symbol cluster for error, memory and negative indicators.
Features: 4 function calculator with percentages, delta percent, backspace, change sign, square root and four function memory.  Double-zero entry key and switches for floating/fixed mode and the number of decimal points.
Age: c1986
Manufacturer: Casio Computer Corp.  Made in Japan.  No serial number that I can find.  Model suffix (B) means this is probably a revision.


A quality feeling calculator that I'm tempted to use on my desk today.  Very sound logic except for the lack of input suppression.  My example has a secondary rear sticker in Japanese and English cautioning you about the correct battery polarity.

Components: 1 x cpu: Hitachi HD38401A  6A 15 (the 15th day/batch of January 1986?), 36 pin DIL, 0.6" width
1 x display: Single flat glass tube, ten digit VFD with symbol cluster
2 x transistor
10 x diodes
8 x capacitors
4 x resistors
1 x transformer; TC-30 5Y TDK
Boards: The keyboard and switch assembly is attached to the front with ten screws and to the main cpu board by a 17-way and 13-way ribbon cable respectively.  The cpu board (A21870-1) is fixed to the base by three screws.
Construction: Remove the four screws from the base and the font lifts off easily; hinge from the bottom so you do not stress the connecting cables.

Logic comments: The (C) button is used to clear last entry of a number and (AC) to clear the whole calculator.
Overflow on number input is not suppressed, typing in an eleven digit number results in an error state which can be recovered by using backspace (>) key.
An overflow error results in the number and an "E" in the symbol cluster to the far left.  Number is not recoverable using (>) or (C)
Divide by zero results in a  "E" as above and  is not recoverable.
There is constant on all multiply and divide only
Square roots of negative numbers are allowed but show an "E" which is recoverable using (>) or (C)
Memory store is indicated by an "M" in the symbol cluster to the far left.
Negative numbers are indicated by a "-" in the symbol cluster to the far left thereby allowing full ten digit negative numbers
There is a decimal switch for floating (F), round down (CUT), round (5/4) and round up (UP).
There is a decimal point switch for 6,4,3,2,1,0 and two-decimal financial input mode.  The latter is like a cash register as keying in (1)(2)(3) result in the number 1.23
The delta percent key marks up; to add 10% tax to 2.50 key in (2)(.)(5)(X)(1)(0)(delta-%) which gives "2.75"
The change sign key can be used in mid number entry

The picture of the inside is taken with the keyboard and front assembly below.  The two wide green ribbon cables can be seen connecting into the main board.

Most of the components are devoted to generating the high voltage needed for the VFD - these can be seen around the cables coming into the left hand side.


An edge on view shows the prominent lift for the display and the slim main body.