Busicom HL21

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Technologically seen, a rather uninteresting machine from the 1960s coming from Japan. What it makes interesting, is the manufacturer: Busicom, as many other firms at that time too, started to develop or to build electronic calculators. They asked the young american firm "intel" to design a chip set for this purpose. The result was the "MCS-4", a chip set consisting of four integrated circuits. The cpu-chip of this, the "i4004" is what today is accepted as the first microprocessor in the world. In the beginning the copyright was at busicom, as this was a custom design. Later, intel bought the copyright back and was now allowed, to sell the chip set to other customers.

Entry register with squareroot(2)

The picture above shows the result of an interesting calculation. The square root of the number 2. But in contrast to the normal algorithm, in german called the "Töpler-Algorithmus" the result is not in the rotation counter, it is in the entry register of the machine. This algorithm needs only two registers, and it was used in the beginning of electronic calculators, for example in the DENON DEC 61A4. At a time, when some flipflops had a noticeable price, such an algorithm allowed significant reduction of costs.