Texas Instruments TI-51-III

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: Red  
    Display technology: Light-emitting diode 
Size: 5½"×3"×1½" Display size: 8+2 digits
Weight: 6 oz    
    Entry method: Algebraic with precedence 
Batteries: 2×"AA" NiCd Advanced functions: Trig Exp Lreg 
External power: AC-9132 adapter (5.7VAC 240 mA)   Memory functions: +/-/×/÷ 
    Programming model: Partially merged keystroke 
Precision: 11 digits Program functions:  
Memories: 10(8) numbers Program display: Keycode display  
Program memory: 32 program steps Program editing: Overwrite capability  
Chipset:   Forensic result: 9.007726486  

ti51-iii.jpg (26988 bytes)Does this one look familiar? If you cannot discover a difference between this calculator and the TI-55, you're not alone. As far as I can tell, the TI-51-III is identical to the TI-55, the only difference being the model number. Oh, and the fact that the TI-51-III was produced mostly in Europe (presumably for the European market?) whereas the TI-55 is more a North American model.

The TI-51-III, at least inasmuch as its model number is concerned, is the last of a proud line of scientific calculators. After (or along with?) the SR-50 and SR-50A, Texas Instruments also began producing the SR-51, and later, the SR-51A scientific calculators. Then came the SR-51-II and eventually, the TI-51-III, shown on this page. Of all these calculators, only the TI-51-III is programmable; however, it represented a trend, as Texas Instruments added a minimal program capability (no branching, conditionals, or any other advanced program features) to many contemporary scientific models.

As the two calculators are identical, all TI-55 programs run fine on the TI-51-III. This includes programs that utilize the RST instruction, along with the fact that the calculator stops on errors, to implement simple loops. One such program I wrote for the TI-55 calculates the factorial. It is reproduced here for the sake of completeness. After entering the argument, hit RST, then R/S; when the program stops with an error, hit CLR RCL 0 to retrieve the factorial result:

00 51	STO
01 01	1
02 34	1/x
03 61	RCL
04 01	1
05 55	×
06 51	STO
07 00	0
08 43	(
09 61	RCL
10 01	1
11 65	-
12 01	1
13 44	)
14 87	RST