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. However, by sacrificing some speed and accuracy, Sinclair used clever algorithms to run scientific operations on a chip with room for just 320 instructions. Instead of an "equals" button, the or 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. The build time was advertised as being around three hours, and required a
soldering iron and a pair of cutters. In January 1975, the kit was available for , half the price at the time of introduction a year earlier, It was larger than the Scientific, at , and used a larger
PP3 battery, but could also be powered by
mains electricity. It also lacked functions for the
natural logarithm and
exponential function. However, included with the calculator was a library of over 120 programs that performed common operations in mathematics, geometry, statistics, finance, physics, electronics, engineering, as well as fluid mechanics and materials science. There were over 400 programs in the full Sinclair Program Library.
Calculations using the Sinclair Scientific The Sinclair used a slightly altered
Reverse Polish Notation method; lacking an enter key, the operation keys enter a number into the appropriate register and the calculation is performed. For example, (1+2) × 3 could be calculated as: to give the result of (, or 9). The key performs a clear; pressing it sets the calculator to a state with zero in the internal registers. Pressing "C" followed by number keys then effectively adds the number entered to the zero and stores it internally to be worked on in subsequent calculations. If the key is pressed instead, the number is subtracted from zero, effectively entering a negative number. All numbers are entered in scientific notation. After entering the mantissa part of the number, the "E" exponent key is pressed prior to entering the integer exponent of the number. The task of ordering the operations is placed on the user, and there are no bracket keys. The display shows only five digits, but six digits can be entered. As an example 12.3×(−123.4+123.456) could be entered as for a displayed result of (representing , or 0.68880). Four constants are printed on the calculator case for easy reference. For converting to and from base 10 logarithms and natural logarithms, the natural logarithm of 10 (2.30259) and e (2.71828) are printed on the case. (3.14159) and 57.2958 (180 / ) are also on the case for trigonometry calculations. There was not enough internal memory to store these constants internally. Angles are computed using radians; degree values must be converted to radians by dividing by 57.2958. As an example, to calculate 25 sin (600×0.05°) one would enter to get a result of (representing 12.5 which is equal to 25 sin(30°) ). Sine is selected with the combination of the key followed by the key. The (down) and (up) arrow keys are function select keys. The four operation keys (, , and ) all have two other functions, activated by using one of the arrow keys. The functions available are sine, arcsine, cosine, arccosine, tangent, arctangent, logarithm and antilogarithm. == References ==