Casio fx-4200P

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: 1988  Display type: Alphanumeric display  
New price:   Display color: Black  
    Display technology: Liquid crystal display 
Size: 5"×3"×½" Display size: 12 characters
Weight: 4 oz    
    Entry method: Algebraic with precedence 
Batteries: 1×"CR-2032" Lithium Advanced functions: Trig Exp Hyp Lreg Cmem 
External power:   Memory functions: +/- 
    Programming model: Formula programming 
Precision: 11 digits Program functions:  
Memories: 26 numbers Program display: Formula display  
Program memory: 279 program steps Program editing: Formula entry  
Chipset:   Forensic result:  

fx4200p.jpg (24005 bytes)A very interesting Casio calculator that has "memo storage" for text, data, or formulae (qualifying the calculator as a programmable model.) Although it has a fair bit of storage (279 steps) individual formulae can only be up to 63 steps long, there are no conditional or branching instructions, and one formula cannot refer to another as a subprogram. This limits the calculator's capabilities, making it yet another beast on which a sophisticated problem, like my favorite programming example, calculating the value of the Gamma function, cannot be solved with a simple program.

That said, Stirling's formula fits easily into the calculator's memory. The version I am presenting here operates on the most recent calculation result; this method avoids prompting by the calculator for the value of any variables that occur in the formula: