Radio Shack EC-4021

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: 5½"×3"×½" Display size: 10(8+2) digits
Weight: 3 oz    
    Entry method: Algebraic with precedence 
Batteries: 2×"LR44" button cell Advanced functions: Trig Exp Hyp Sdev Cmem 
External power:   Memory functions:
    Programming model: Partially merged keystroke 
Precision: 11 digits Program functions:  
Memories: 3 numbers Program display:  
Program memory: 40 program steps Program editing:  
Chipset: Sharp LI3301A   Forensic result: 9.0000156204  

ec4021.jpg (23963 bytes)Yet another pawn shop find: an old Radio Shack EC-4021 calculator, an OEM Sharp model. A very simple calculator this is; only 40 program steps, 3 memories, and no program control instructions of any kind. It is also one of those annoying models that zeroes the display when you switch to program entry mode, making it unnecessarily difficult to enter algorithms that yield an error on an argument of zero. Needless to say, you won't be able to implement a complex algorithm like that of the Gamma function on this beast. Here is instead a version of Stirling's formula, which calculates the extended factorial of the number on the display with quite good accuracy: