Radio Shack EC-4004

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+2 digits
Weight: 4 oz    
    Entry method: Algebraic with precedence 
Batteries: 1×"CR-2025" Lithium Advanced functions: Trig Exp Hyp Lreg Cmem 
External power:   Memory functions: +/-/×/÷ 
    Programming model: Fully-merged keystroke entry 
Precision: 11 digits Program functions: Cond  
Memories: 7 numbers Program display:  
Program memory: 38 program steps Program editing:  
Chipset: Casio fx-3600P   Forensic result: 9.0000157179  

ec4004.jpg (24557 bytes)The EC-4004 is a Radio Shack OEM version of the venerable Casio fx-3600P programmable calculator.

At first, I seriously underestimated the capabilities of this machine. 38 program steps? A conditional loop-to-start instruction as the only means of branching? Surely, that's not enough to do anything useful, certainly not something as complex as my favorite programming example, the Gamma function.

Well, I was wrong. This machine is more capable than I thought, due in part to the fact that it offers four-function memory arithmetic on its six K-registers. Moreover, these 3-keystroke instructions count only as a single step in program memory. Impressive! A fellow calculator enthusiast already sent me an implementation of the incomplete Gamma function (see my fx-3600P page for the listings.)

Of course, if you don't want to key in a complex and slow program, and you can use results with more limited accuracy, you can still make use of Stirling's formula: