.

Type, Precision, Input mode | Scientific, 5 BCD digits, exponent ±99, Reverse Polish Notation |

Programmable | No |

Memory | None |

Display | 9 digit 7 segment red LED |

Special features | Simple 2-level-stack RPN |

Original Pricing, Production | August 1974, approx. 32 UK-Pound ($119.95) |

Batteries | 4x AAA, no external powr supply |

Dimensions | Length 11.1cm, Width 5cm, Height 1.8cm |

Links | Sinclair
Scientific
Programmable. Planet Sinclair. Retrokit. Operating Manual (PDF, 18 pages, English) and Assembly Manual (PDF, 11 pages, English) Vintage Electronic Calculator Manuals. |

Comment | A very unusual device: It is quite small and of
quite
cheap making. This display can only be read directly from the front. It
offers
only 5 digits of precision but an exponential range of ±99. There are trigonometric functions and their inverse as well as log and antilog - but no square root. Powers and roots must be calculated by using log/antilog. Angles are measured in Radians, log and antilog are base 10. There is no decimal point key. Rather, the decimal point is hardwired to appear after the first digit. To enter a number like 125.2 exponential form must be used: Enter "1252 E 2" and the result will be "1.252 E 02". There is no ENTER key either so in order to start a new calculation "C" must be pressed to erase both the X and Y register. Now enter the first number and press + (or - to get a negative number. Btw, did I mention that there is no CHS or +/- key? Undoubtedly a marvel of reduced hardware!). Finally, enter the second number and press the operation key. To enter numbers with small negative exponent leading zeros can be used. Ie. to enter 0.0375 press "00375" and after hitting + the result will be a normalized "3.75E-02". To enter numbers with larger negative exponent use the minus key. Ie. to enter 2E-17 press "2 E - 17". Every operation pushes the result into the Y register! Ie. "2 3 +" puts the result of 5 in both X & Y. If + is pressed again the result will be 10. This also applies to the transcendental functions so that you cannot calculate 1+sin(0.5) from left to right because executing the sine will overwrite the 1 in the Y register. The sequence to calculate the above would be "05 SIN 1 +". The result is 1.4799 whereas the correct value would be 1.4794. The valid input range for log is [1.0..1E99]. Outside this range the result will always be 1. Similarly, the antilog of a negative number will ignore the sign. The valid input range for sin, cos and tan is [0...p/2]. The manual carefuly states the (lack of) accuracy of various operations, ie. "The arc cosine of values between 0.001 and 0.9995 will have an accuracy of better than 0.001." This is already pretty bad but keep in mind that those 0.001 are an absolute not a relative value! Ie. acos(0.9995) yields 0.032 but the correct result is 0.0031624. |

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