Casio FX-11

Casio FX-11 Calculator

The Casio FX-11 is a large, bulky scientific calculator from 1974. It measures approximately 95mm x 150mm x 30mm (width, height, depth) and weighs 222g without batteries. The calculator requires 4 AA batteries or can use an AC adapter.

The FX-11 has a smooth white plastic two-piece case. The display filter sits flat in its own raised section. Below this is a recessed metallic sticker with the Casio name. The keyboard has matt black plastic with white printed labels. The keys have a soft click and fast return bounce.

This calculator has an 8-digit vacuum fluorescent display (VFD) in blue. There is no 9th digit on the display. The digits use a small “0” notation, where the 0 digit has a reduced central bar. This was likely done so a failed segment would not affect legibility.

The FX-11 performs the four standard arithmetic functions plus square root, powers, trigonometric and transcendental functions. However, it lacks any arc abilities. The transcendental and trigonometric functions are only accurate to 5 decimal places.

Power functions allow raising a number to a positive integer exponent without pressing equals. For example, 2^8 is entered as 2, x^y, 8. Pi is limited to 6 decimal places.

There is a constant function on all four arithmetic operations. Input overflow is suppressed, ignoring extra digits. Negative numbers show a minus sign taking the leftmost display digit. So the largest negative number is 7 digits.

Overflow and divide by zero display “oooooooo” without recovery. Square roots of negative numbers result in a positive number.

Logic and Other Details:

  • C clears the last number entered, AC clears the entire calculator
  • Automatic constant on the four basic arithmetic functions
  • Input overflow is suppressed, 9th digit ignored
  • Negative numbers shown with – taking leftmost digit, limiting negatives to 7 digits
  • Overflow shows oooooooo without recovery
  • Divide by zero displays oooooooo without recovery
  • Square roots of negative values give a positive result
  • Transcendental and trig functions to 5 decimal places
  • Power raising for positive integers only, no equals needed
  • Pi limited to 6 decimal places

The Casio FX-11 is an early scientific calculator with a bulky white plastic case and blue VFD display. It has basic scientific functions but limited accuracy and lack of overflow recovery make it fairly rudimentary. The unusual “small zero” display provides a window into early calculator design. For collectors, the FX-11 is an interesting example of Casio’s scientific calculators before they adopted a more modern form and feature set.

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