Texas Instruments TI-92
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 |
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Texas Instruments TI-92
What a nice change after all those uninspiring, schoolboard-designed graphing calculators that I got my hands on in recent months! The TI-92 is at last a serious, no-compromise engineering tool, a true competitor to (if not outright a better machine than) top-of-the-line Hewlett-Packard models.
The TI-92 is a handheld (ahem; it does weigh a hefty pound and a quarter) machine with symbolic algebra, calculus, geometry, and other capabilities. I knew this was an interesting machine, but I admit I was still stunned by the capabilities it delivers. For instance, if you ever wanted to know the factorial of 100, the TI-92 tells you easily: it's 93,326,215, 443,944,152,681,699,238,856,266,700,490, 715,968,264,381,621,468,592,963,895,217, 599,993,229,915,608,941,463,976,156,518, 286,253,697,920,827,223,758,251,185,210, 916,864,000,000,000,000,000,000,000,000.
See what I mean by no compromise?
I've already spent a few hours exploring the capabilities of this machine. I also spent a few hours using this machine, further exploring my favorite computation example, the Gamma function. Surprisingly, the TI-92 does not have a built-in implementation of this important function; it only calculates the factorial for non-negative integers. The challenge, then, is to create a Gamma function implementation that behaves much like the TI-92's built in functions; i.e., an implementation that is accurate, yields symbolic and/or integer results when possible, and executes efficiently.
My explorations are still a work-in progress, but here is a fresh variant on Stirling's approximation that calculates the logarithm of the Gamma function on the TI-92:
:lnГ(z) :Func :If real(z)<0 or real(z)<10 and fPart(z)≠0 and fPart(z)≠.5 Then :Return lnГ(z+1)-ln(z) :ElseIf imag(z)=0 and real(z)<450 and fPart(z)=0 Then :Return ln((z-1)!) :ElseIf imag(z)=0 and fPart(z)=.5 Then :If iPart(z)>0 Then :Return lnГ(z-1)+ln(z-1) :Else :Return ln(√(π)) :EndIf :Else :Return (z-.5)*ln(z)-z+.5*ln(2*π)+1/12/z-1/360/z^3+1/1260/z^5-1/1680/z^7+1/1188/z^9 :EndIf :EndFunc