Sinclair Scientific

The Sinclair Scientific calculator was a 12-function, pocket-sized calculator, selling for about $100 in the USA and around £45 in the UK. It was introduced in 1974 and sold in both kit and assembled forms ["An Engineer's Notebook", CME journal, April 1974, p24.] . It used RPN, In 1977 a revised model, the "Scientific Programmable", was released at £29.95. The Scientific Programmable Mark 2 was later released, reducing the price to £17.22.

Power was supplied by four AAA sized alkaline cells. A common failure mode of these calculators was breakage of the battery contacts, but Sinclair was quick to respond by refurbishing any calculator with this problem for free (although you did have to pay the shipping to them).

Numbers were displayed on the 8 digit LED display in scientific format with a 5 digit mantissa and a 2 digit exponent.

An ingenious aspect of the design which showed Sinclair's inventiveness was that the machine made use of what was originally a 4-function calculator chip. Sinclair realised that by using RPN and allowing a reduced precision of 4 or 5 significant figures displayed in scientific notation, the algorithms for scientific functions could be redesigned and compacted to fit in the same programmable space on the chip. This allowed Sinclair to adapt the relatively low-cost processor and produce an 'electronic slide rule' that fitted easily in a shirt pocket, at a price that even impecunious students could afford.

As a consequence of the compacted logical design and in common with many ground-breaking inventions, operation was a little idiosyncratic, but amazingly flexible with familiarity. Keys trebled up on functionality, important constants were printed on the case below the display, and the instruction book contained many useful keystroke sequences for common functions that were otherwise absent from the device - thus making the calculator much more versatile than the keyboard at first suggests.

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