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: 7-segment
New price:  
Display color: Red
    Display technology: LED
Size: 3"×6"×1½" Display size: 10+2 digits
Weight: 9 oz    
    Entry method: Algebraic with precedence
Batteries: BP-1 (3×"AA" sealed NiCd) Advanced functions: trg, hyp, exp, log, drg, dms, stat
External power: TI AC-9130 adapter (8.2V AC 225mA) Memory functions: +/-/×/÷
I/O: N/A    
    Programming model: N/A
Precision: 12 digits Program functions: N/A
Memories: 1 number
Program display: N/A
Program memory: N/A
Program editing: N/A
Chipset:   Forensic result:  

sr50.jpg (21992 bytes)The SR-50 was Texas Instrument's first full-featured scientific calculator. It was the company's response to the challenge presented by the Hewlett Packard 35.

The SR-50 is a sleek, very well designed scientific calculator with a large, 10+2 digit display. Unlike later Texas Instruments models of similar appearance that felt like a creaky box of cheap plastic, the SR-50 has a solid, instrument-quality feel.

Despite its historic significance, the SR-50 would normally fall outside my main area of interest, programmable calculators. However, once again I was unable to resist when I was presented with the opportunity to obtain a specimen in excellent condition (as the image on the right shows, the silver trim is entirely intact, which is quite a rarity) at a bargain price.

There is also another reason: the SR-50 belongs to a family of four calculators that are closely related to the first line of programmable calculators (including the SR-52 and SR-56) from Texas Instruments. Of these, the SR-50 and SR-51 have an almost identical appearance; the same is true for the SR-50A and the SR-51A. However, it is the SR-51 and SR-51A that have a connector in the battery compartment which can be used with the PC-100 printer cradle, when the printer is switched to SR-52 compatibility mode. I don't have any documentation with my SR-51 or SR-51A (I received the SR-51 as a gift, and obtained my SR-51A by chance, advertised as non-working, along with an SR-52) but the lack of any printer-related keys on its keyboard appear to suggest that printer compatibility might not have been officially supported. It also makes one wonder: are there any other functions this calculator may have that aren't accessible from its keyboard? If only I knew the specifications for the bidirectional PC-100 printer interface...

The SR-51A was also the first calculator I ever saw that had a built-in random number generator. One also gets the feeling that its conversion functions (2nd followed by a two-digit number) are in fact implemented as ROM-based programs that are not unlike the keystroke programs on programmable models.

Incidentally, the SR-51 had two other variants, however, these more properly belong to the next generation of Texas Instruments scientific calculators, with a much cheaper construction. The SR-51-II is a non-programmable scientific calculator, but the TI-51-III is actually identical to the TI-55, with minimal programmability.