Two species calculator

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Two-species calculator is the name for a mechanical computing device for addition and subtraction .

After the Indian place value notation with Arabic numerals had prevailed, attempts were made in many places to mechanize recurring arithmetic operations; the closest thing was to mechanize addition.

A two-species calculator based on a wheel drive was developed by Blaise Pascal around 1642. The tens carried over automatically. The last two digits had a non- decimal division that the currency units equivalent in England and France. A replica of the device made in 1937 is in the Mathematical-Physical Salon in the Dresden Zwinger .