Texas Instruments TI-55-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: Black  
    Display technology: Liquid crystal display 
Size: 6"×3"×½" Display size: 8+2 digits
Weight: 4 oz    
    Entry method: Algebraic with precedence 
Batteries: 2×"LR44" button cell Advanced functions: Trig Exp Hyp Lreg Cmem Units 
External power:   Memory functions: +/-/×/÷/^ 
I/O:      
    Programming model: Partially merged keystroke 
Precision: 11 digits Program functions:  
Memories: 8(1) numbers Program display: Keycode display  
Program memory: 56 program steps Program editing: Overwrite capability  
Chipset:   Forensic result: 9.114640577  

ti55iii.jpg (24054 bytes)Does it look familiar? Other than some minor cosmetic changes, I really see no difference between this calculator and the Texas Instruments TI-55-II. Oh, well, one of them was made in Taiwan, the other in the USA, but then what? (Interestingly, the one made in Taiwan is the one with a better keyboard.)

Functionally, the two calculators are identical. Like the TI-55-II, the TI-55-III is an "almost programmable"; it has capacity to store up to 56 program steps, but no control transfer or conditional instructions are provided. Also, just like on the TI-55-II, loops are not possible even with the RST button, because it stops program execution (in contrast, on the TI-55 or TI-60, RST causes execution to continue at step 00, so simple loops are possible.)

Well, in the absence of anything more sophisticated, here it is again, a simple program that implements Stirling's formula that approximates the extended factorial:

00  61    STO
01  00    0
02  65    ×
03  02    2
04  65    ×
05  91    π
06  95    =
07  13    √
08  65    ×
09  71    RCL
10  00    0
11  45    yx
12  71    RCL
13  00    0
14  55    ÷
15  71    RCL
16  00    0
17  41    INV
18  44    lnx
19  65    ×
20  53    (
21  71    RCL
22  00    0
23  17    1/x
24  55    ÷
25  01    1
26  02    2
27  85    +
28  01    1
29  95    =
30  22    RST