Sharp EL-5100

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: Alphanumeric display  
New price:   Display color: Black  
    Display technology: Yellow LCD 
Size: 2½"×7"×½" Display size: 24 characters
Weight: 6 oz    
    Entry method: Formula entry 
Batteries: 3×"LR44" button cell Advanced functions: Trig Exp Hyp Lreg Cmem 
External power:   Memory functions:
    Programming model: Formula programming 
Precision: 12 digits Program functions:  
Memories: 11 numbers Program display: Formula display  
Program memory: 80 program steps Program editing: Formula entry  
Chipset:   Forensic result: 8.999981534  

el5100.jpg (30663 bytes)The Sharp EL-5100 is a vintage calculator with formula storage. Up to 5 simple algebraic formulae (80 steps in total length) can be stored and executed. The machine offers no branching or conditionals, so loops or iterative programs cannot be entered. Nevertheless, it's quite an interesting and useful beast; the one I just received was obviously much loved by its previous owner.

I have not yet tried shoehorning my favorite example, the Gamma function into this calculator's formula memory; thanks to ten registers that can be used to store constants, it just might be possible to enter an expression of that complexity. For now, here's an improved version of Stirling's formula, one which provides a very good approximation of the Gamma function for large arguments (and a reasonable approximation for small ones):