Alright, I admit: when I first saw a sufficiently detailed picture of the fx-191 to realize that this device in fact integrates an electronic ruler with a programmable calculator, my eyes almost popped out.

Yes, that's right: the calcuruler indeed has an electronic ruler, a 6" long strip of an LCD display alongside its ruler edge. Curious, to say the least! The device also integrates ruler-specific functionality: in particular, it offers the ability to measure a triangle, and then compute its area and one of its angles.

As a programmable calculator, the fx-191 is a somewhat mediocre device. It has the same limited programming model found in many low-end Casio programmables; this is compounded by the fact that the machine has only one memory register, and doesn't have those memory arithmetic operations that are really the "saving grace" for other Casio models.

Not quite as useful as an implementation of the Gamma function, the following simple program, which computes the factorial, better demonstrates this calculator's limited programming model. The programmer has to work around idiosyncrasies such as the fact that conditional instructions force execution to resume at the beginning of program memory, or that using memory arithmetic causes any pending operations to be evaluated first. Nevertheless, this simple program is not altogether useless:

Min
×
(
MR
-
1
)
X>0
1
=