Texas Instruments TI-92 Plus
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 Plus
Texas Instrument's domination of the educational calculator market continues. The TI-92 Plus is yet another reminder of this fact: a no-nonsense, no compromise device that is halfway between a calculator and an all-purpose learning tool. Indeed, a look at Texas Instrument's educational Web site makes it clear that now, having conquered science classes throughout the United States and elsewhere, they're busy developing applications that will be used (or so they hope) by students of history, political science, and other subjects.
To be sure, the TI-92 Plus is a good, thoroughly well-designed machine. In fact, this machine (along with its cousin, the TI-89) is truly the only non-RPN computer/calculator that gives me the same sense of solid well-designedness that used to be the exclusive domain of Hewlett-Packard machines.
The reason: a well designed implementation that fully integrates symbolic and numerical calculations, real and complex-valued functions, user-defined and built-in functions. It isn't on every calculator that you can define a Gamma function implementation that produces accurate results for both real and complex arguments, and exact results for special arguments such as integers and half integers.
This is exactly what my demonstration program does below. Hopefully useful, in view of the glaring omission, the lack of a built-in Gamma function implementation on this otherwise hugely capable machine. This program is similar to the program I wrote for the TI-92, except that here, I use the Lanczos-approximation as opposed to Stirling's formula to compute a numerical result:
:lnГ(z) :Func :If real(z)<0 and fPart(z)≠0 and fPart(z)≠.5 Then :Return lnГ(z+2)-ln(z*(z+1)) :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 ln(2.5066282756348+225.52558461918/z-268.2959738413/(z+1)+ 80.903080693462/(z+2)-5.0075786397052/(z+3)+ .011468489543478/(z+4))+(z-1/2)*ln(z+4.65)-z-4.65 :EndIf :EndFunc