Editing Sinclair Scientific (section)

===Sinclair Scientific===
The HP-35 used five chips, and had been developed by twenty engineers at a cost of a million dollars, leading the Texas Instruments engineers to think that Sinclair's aim to build a scientific calculator around the TMS0805 chip, which could barely handle four-function arithmetic, was impossible.<ref name=eng>{{cite web |url=http://files.righto.com/calculator/sinclair_scientific_simulator.html |title=Reversing Sinclair's amazing 1974 calculator hack - half the ROM of the HP-35 |last=Shirriff |first=Ken |access-date=9 December 2013}}</ref><ref name=reg>{{cite web |url=https://www.theregister.co.uk/2013/09/02/google_chap_reverse_engineers_sinclair_scientific_calculator/ |title=Google chap reverse engineers Sinclair Scientific Calculator |work=The Register |last=Sharwood |first=Simon |date=2 September 2013 |access-date=9 December 2013}}</ref> However, by sacrificing some speed and accuracy, Sinclair used clever algorithms to run scientific operations on a chip with room for just 320 instructions.<ref name=eng/> [[Mathematical constant|Constants]], rather than being stored in the calculator, were printed on the case below the screen.<ref name=eng/>

It displays only in scientific notation, with a five digit [[Significand|mantissa]] and a two digit [[Exponentiation|exponent]], although a sixth digit of the mantissa was stored internally.<ref name=eng/> Because of the way the processor was designed, it uses [[Reverse Polish notation]] (RPN) to input calculations.<ref name=eng/> RPN meant that the difficult implementation of brackets, and the associated recursive logic, was not necessary to implement in the hardware, but the effort was instead offloaded to the user.<ref name=rpn>{{cite web |url=http://www.calculator.org/rpn.aspx |title=What is Reverse Polish Notation? |publisher=calculator.org |access-date=10 December 2013}}</ref> Instead of an "equals" button, the {{key top|+}} or {{key top|&minus;}} keys are used to enter the initial value of a calculation, followed by subsequent operand(s) each followed by their appropriate operator(s).

To fit the program into the 320 words available on the chip, some significant modification was used.<ref name=eng/> By not using ordinary [[floating point]] numbers, which require many instructions to keep the decimal point in the right place, some space was freed up.<ref name=eng/> Trigonometric functions were implemented in about 40 instructions, and [[inverse trigonometric functions]] took almost 30 more instructions.<ref name=eng/> Logarithms are about 40 instructions, with anti-log taking about 20 more.<ref name=eng/> The code to normalize and display the computed values is roughly the same in the TI and Sinclair programs.<ref name=eng/>

The design of the algorithms meant that some calculations, such as [[Inverse trigonometric function|arccos]]0.2, could take up to 15 seconds, whereas the [[HP-35]] was designed to complete calculations in under a second.<ref name=eng/> Accuracy in scientific functions was also limited to around three digits at best, and there were a number of bugs and limitations.<ref name=eng/>

Ken Shirriff, an employee of [[Google]], reverse engineered a Sinclair Scientific in 2013 and built a simulator using the original algorithms.<ref name=eng/><ref name=reg/>

====Assembly kit====
The assembly kit consisted of eight groups of components, plus a carry case.<ref name=pm>{{cite journal |url=https://books.google.com/books?id=g-IDAAAAMBAJ&pg=PA5 |journal=Popular Mechanics |date=January 1975 |page=5 |title=What does it take to build the world's smallest scientific calculator?}}</ref> The build time was advertised as being around three hours, and required a [[soldering iron]] and a pair of cutters.<ref name=pm/><ref name=ns>{{cite journal |url=https://books.google.com/books?id=FS6D5VL2qo4C&pg=PA639 |title=Sinclair Scientific assembly kit |date=December 1975 |journal=New Scientist |page=639}}</ref> In January 1975, the kit was available for {{USD|49.95}}, half the price at the time of introduction a year earlier,<ref name=pm/> and in December 1975 it was available for {{GBP|9.95}}, less than a quarter of the introductory price.<ref name=ns/>