Casio fx-50F

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: 1987  Display type: Numeric display  
New price:   Display color: Black  
    Display technology: Liquid crystal display 
Size: 5½"×3"×½" Display size: 10+2 digits
Weight: 3 oz    
    Entry method: Algebraic with precedence 
Batteries: 1×"GR927" button cell Advanced functions: Trig Exp Hyp Lreg Ab/c Cmem BaseN Const Eqlib 
External power: Solar   Memory functions: +/-/×/÷ 
    Programming model: Fully-merged keystroke entry 
Precision: 12 digits Program functions: Cond  
Memories: 7 numbers Program display:  
Program memory: 29 program steps Program editing:  
Chipset:   Forensic result: 9.00001568547  

fx50f.jpg (27174 bytes)Here is a calculator that, despite its small program memory and limited programming model, is nevertheless a machine I almost like. Why? Simple: because it is one of the few programmable models in existence that runs from solar energy.

No, I'm not a nutty environmentalist who believes that every electric toothbrush must come equipped with its own solar panel. But there's a great deal of elegance to a circuit, a functioning computer in fact, that uses so little energy, ambient light in a moderately lit room is sufficient for it to operate.

That said, 29 program steps is a very small amount of program space. Were it not for this machine's fully merged programming model, it'd be pretty close to useless. With merged program steps, and full memory arithmetic however, it is possible to squeeze moderately complex algorithms into program memory. One example is a program I wrote that computes the Gamma function, to 6+ digits of precision, for any argument; it uses an iterative loop to compute more accurate results for small or negative arguments:

K3: 1/12 (0.0833333333333)
K4: 2×π  (6.2831853072)
Kin+ 1
Kin 2
Kout 2
Kout 4
Kout 2
Kout 3
Kout 2
x-K 1