Casio fx-191

Datasheet legend
Ab/c: Fractions calculation
AC: Alternating current
BaseN: Number base calculations
Card: Magnetic card storage
Cmem: Continuous memory
Cond: Conditional execution
Const: Scientific constants
Cplx: Complex number arithmetic
DC: Direct current
Eqlib: Equation library
Exp: Exponential/logarithmic functions
Fin: Financial functions
Grph: Graphing capability
Hyp: Hyperbolic functions
Ind: Indirect addressing
Intg: Numerical integration
Jump: Unconditional jump (GOTO)
Lbl: Program labels
LCD: Liquid Crystal Display
LED: Light-Emitting Diode
Li-ion: Lithium-ion rechargeable battery
Lreg: Linear regression (2-variable statistics)
mA: Milliamperes of current
Mtrx: Matrix support
NiCd: Nickel-Cadmium rechargeable battery
NiMH: Nickel-metal-hydrite rechargeable battery
Prnt: Printer
RTC: Real-time clock
Sdev: Standard deviation (1-variable statistics)
Solv: Equation solver
Subr: Subroutine call capability
Symb: Symbolic computing
Tape: Magnetic tape storage
Trig: Trigonometric functions
Units: Unit conversions
VAC: Volts AC
VDC: Volts DC
Years of production:   Display type: Numeric display  
New price:   Display color: Black  
    Display technology: Liquid crystal display 
Size: 2½"×9"×½" Display size: 8+2 digits
Weight: 6 oz    
    Entry method: Algebraic with precedence 
Batteries: 2×"CR-2032" Lithium Advanced functions: Trig Exp Sdev Ab/c Cmem 
External power:   Memory functions: +/- 
    Programming model: Fully-merged keystroke entry 
Precision: 11 digits Program functions: Cond  
Memories: 1 numbers Program display:  
Program memory: 52 program steps Program editing:  
Chipset:   Forensic result: 9.0000157179  

fx191.jpg (35765 bytes)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: