Jido Soroban (Automatic abacus)

Yazu Ryoichi conducted research on calculators and invented a mechanical calculating machine "Jido Soroban" (Automatic Abacus). After obtaining a patent, he manufactured Japan's first mechanical desktop calculating machine in 1903. It is said that the Yazu's machine was superior to those in overseas.

After dropping out of junior high school, Yazu learned the basic subjects at a private school, and did research on flight and calculators. Takahashi, who was the editor in chief of the Fukuoka Nichinichi Shimbun newspaper, was greatly impressed by Yazu's abilities, and wrote a letter of introduction to Mori Rintaro (Mori Ogai), who was a medical officer in the Kokura 12th Medical Corps. Ogai also was deeply impressed by Yazu's character and research, and worked as a go-between with the professors of Tokyo Imperial University. In March 1902, Yazu applied for a patent on his automatic abacus, and completed a version made entirely of metal. The patent was granted in January 1903, and in March a shop was established, and the first calculator in Japan was manufactured. This was a manual desktop calculator which perfofmed decimal arithmetisc operations using a single cylinder and 22 gears with biquinary number setting for input like an abacus.. The price was high -- 250 yen for one machine -- but more than 200 were sold. The profits from the sale were invested into Yazu's airplane research. Yazu Ryoichi died young, at the age of 31.

One of Yazu's calculators was preserved by the Hisatomi Family of Buzen Sho-e (the descendants of Yazu Ryoichi's sister), but today this machine has been entrusted to the City of Kitakyushu. Mechanical ｃalculating ｍachine "Automatic Abacus", is now preserved at the City of Kitakyushu.