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: LightEmitting Diode Liion: Lithiumion rechargeable battery Lreg: Linear regression (2variable statistics) mA: Milliamperes of current Mtrx: Matrix support NiCd: NickelCadmium rechargeable battery NiMH: Nickelmetalhydrite rechargeable battery Prnt: Printer RTC: Realtime clock Sdev: Standard deviation (1variable 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 


While not a programmable beast, this calculator is one of the most versatile early scientific calculators I've ever seen. In fact, it was this calculator (the very machine pictured here, actually) that got me started on my quest to write an efficient and accurate Gamma function implementation on the programmables I later owned.
In addition to the usual complement of scientific and statistical functions and a pair of storage registers, this calculator has complex arithmetic, three probability distribution functions (Gaussian, Poisson, and binomial), a large number of unit conversions, and of course the infamous Gamma function that I was so obsessed with.
The calculator displays results with ten digits of precision, but uses 12 digits internally. This leads to an interesting quirk. If you have one of these calculators on hand, try typing the following:
9.999999999 EE 99 + 9.9 EE 89 =
The result is 1. But this is a strange kind of 1; take its square root, for instance, and you get 1e50. What happens is that the calculator rounds up 9.99999999999e99 to 1e100 before display. However, since the exponent can only contain two digits, the result in fact becomes 1e00, or 1. Other calculators display an error when this condition occurs, but not the SR4190R. Peculiar, isn't it?
I received this calculator from a good friend in Hungary many years ago (the same friend who owned it back in 1977 or so, when I first saw it.) With a new set of NiCad batteries, the calculator still works perfectly. In fact, I often use it to verify the accuracy of my various Gamma function programs on other vintage calculators!
I have since acquired another Commodore machine, a close relative of the SR4190R: the SR9190R. Apart from a different color scheme, the two calculators look very similar in appearance. However, the SR9190R has not only many more memories (10 in place of the SR4190R's two), it also sports a unique feature: instead of the Gamma function, it calculates its natural logarithm, which of course yields values that the calculator can display for a far broader range of arguments, making it that much more practical for use with reallife problems.