CASIO fx-19

Description

Brand: CASIO
Model: fx-19
Type: Scientific calculator
Picture: CASIO fx-19
Batteries: AA x 4
Lifetime: Introduced: ca. 1976
Terminated: unknown
Notes: A CASIO scientific calculator with a fluorescent display, a slider to switch between modes, and capable of calculating with fractions and statistical operations.

Quite similar to the CASIO fx-29. As far as I can tell the main difference is the layout, the casing and the number of batteries.

The workings of the xy key might be puzzling to users of this calculator. When you enter a (positive) number and press the xy key an intermediate result is shown, being the natural log "ln" of the number entered. To obtain its power enter the value for y and press the = key. My guess is that this calculator uses this formula:
xy = e(y · ln x)
This works nicely for positive values of x but will result in an error when x is zero or less. Not a big problem because powers of negavive numbers behave counter intuitive anyway (producing non-complex results only for integer values of y or fractional values of y with an odd denominator).

This calculator has separate keys for the exponent and the constant π instead of the combined key of most other scientific calculators by CASIO (where the EXP key will enable you to enter the exponent when you first enter digits, and will otherwise enter the constant π).

There’s no INV key, but there is an arc key for the inverse trigonometric functions.

Statistical functions are available when the mode selector slider is all the way to the right.

Peripherals

A power adapter.