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
Years of production:   Display type: Graphical display  
New price:   Display color: Black  
    Display technology: Liquid crystal display 
Size: 5"×9"×1½" Display size:  pixels
Weight: 20 oz    
    Entry method: Formula entry 
Batteries: 4×"AA" alkaline + 1×"CR-2032" Lithium Advanced functions: Trig Exp Hyp Lreg Grph Solv Intg Ab/c Cplx Symb Cmem Mtrx 
External power:   Memory functions:  
I/O: TI-GraphLink™     
    Programming model: Formula programming 
Precision: 14 digits Program functions: Jump Cond Subr Lbl Ind  
Memories: 192(0) kilobytes Program display: Formula display  
Program memory: 192 kilobytes and 702 kilobytes Program editing: Formula entry  
Chipset:   Forensic result: 8.9999999817692  

ti92+.jpg (45069 bytes)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:

: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)
:Return ln(√(π))
:Return ln(2.5066282756348+225.52558461918/z-268.2959738413/(z+1)+