Hewlett-Packard 35 (2)

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Hewlett-Packard produced its first desktop calculator, the 9100A, in 1968, priced at $4,900. The machine built from transistors was programmable, could be used according to Reverse Polish Notation (RPN) logic, and in addition to the four basic arithmetic operations, could also perform calculations with trigonometric, logarithmic and exponential functions. Later, it was suggested that the size of calculators could be dramatically reduced as a result of new technologies, but surveys proved that users do not require hand-held scientific or programmable calculators, because desktop-sized versions are more suitable for such purposes. Despite this, under the influence of Bill Hewlett's vision, they began to design a pocket calculator with scientific functions. The HP-35 was finally completed in 1972, with a price of $395. Using the experience of desktop calculators produced up to that time, it was already considered a classic, four-register RPN calculator, with a capacity of 10+2 digits. It turned out to be an incredible success. Later, minor modifications were made to that model: in 1973, due to easier handling and uniform appearance, the scientific functions were given wider, labeled buttons, until production was finally stopped in 1975, when the normal and programmable successors were already available. .

When it appeared, it was considered special in almost every aspect: neither its size, nor its shape, nor its use were conventional. The smaller-than-average size of modern pocket calculators that perform basic operations, the designed device housing encouraged many other manufacturers around the world to design machines with a similar design. The operations that could be performed by the HP-35 created a new category. Its success clearly showed that there is considerable customer demand for similar machines, so leading circuit manufacturers began to design chips for building cheap scientific machines with similar features, but with simpler operation. RPN logic was also considered unusual, but due to its simplicity and minimal hardware requirements, others also tried to produce machines with similar functionality, such as National Semiconductor published a series of models in 1975-76, some of which were well known in Hungary: for example, the TK-1024 type assembled by Híradástechnika Szövetkezet was in many respects very similar to the HP-35.

Interesting fact: the HP-35 type was also presented at the Budapest International Fair (BNV) in 1973, and of course it became a success in the Communist Block: national companies often chose the unofficial route to get such a machine. At the same BNV, Híradástechnika Szövetkezet presented its pocket calculators manufactured under license from Bowmar, as well as EMG's first calculator with integrated circuit, the HUNOR 81.