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The founder of Casio Computer Co., Ltd., Kashio Tadao, was born in Kureta-mura (now Nankoku City) in Japan, in 1917. After the Great Kanto Earthquake of1923, the whole Kashio family moved to Tokyo at the invitation of an uncle working there. After graduating from high school, Tadao began working as an apprentice to a lathe operator. The factory owner recognized his skills and encouraged him to begin studies at Waseda Koshu Gakko (now Waseda University), whilst still working at the factory. Tadao gained experience in a variety of jobs, making pots, pans, and bicycle generator lamps, and soon earned a reputation for himself and received subcontracts to process parts. In 1946, Tadao set up his own business called Kashio Seisakujo, in Mitaka, Tokyo. The factory he set up was called Kashio Seisakujo and was a small subcontractor factory that made microscope parts and gears. Tadao had three younger brothers, Toshio, Kazuo, and Yukio. Toshio initially worked at the Tokyo office of the Telecommunications Ministry as a technician, building and equipping telegraph and telephone facilities.

As a child, Toshio had admired Edison and always harboured ambitions to become an inventor. When he saw how his young brother toiled everyday, he wanted to help – maybe he could invent something that his brother could produce?

He left his job and joined the fledgling Kashio Seisakujo.

Utilizing his natural inventiveness, Toshio tried out several new ideas. One of these was “the yubiwa (finger ring) pipe.” At that time in postwar Japan, commodities were in short supply, and people smoked their cigarettes down to the very nub. For this reason, Toshio came up with a ring-mounted cigarette holder so that he could also smoke while doing his work. Tadao produced it on a lathe, and their father Shigeru went out to market it. Orders gradually began to pour in and the yubiwa pipe quickly became a hit product. The profits from this invention would later go towards the capital needed for development of a new kind of calculator.

Looking for a new product to follow on from the success of the yubiwa pipe, the Kashio brothers laid eyes on foreign-made electric calculators at the first Business Show held in Tokyo in 1949. Most calculators at that time used mechanical gears or were hand operated with a crank! Electric calculators using a small motor to turn the gears had already appeared overseas but they could not be manufactured in Japan. One of the problems was the shrill noise the gears made when turning. Toshio believed that by replacing the mechanical parts with electrical circuits he could create a much improved calculator.

Tadao and Toshio soon found themselves working all day to make a living, and then spending their evening hours developing the calculator. They demonstrated their prototype to colleagues and responded to feedback in order to improve their invention. After making ten or more prototypes, they completed Japan’s first electric calculator in 1954. The following year, the brothers proudly took their finished product to Bunshodo Corporation, an office supplies trading company.

Unfortunately, the Bunshodo representative told them that their calculator was out of date because it could not do continuing multiplication, wherein a multiplication product could be subsequently multiplied by another number.

Tadao and Toshio returned to the drawing board, working on new prototypes. Around that time, the two youngest brothers quit their jobs and began working at Kashio Seisakujo. In 1956, six years after the start of development, they were close to completing a calculator with a continuing multiplication function when Toshio suddenly declared that he wanted to completely redesign the calculator. The initial design meant potential difficulties for mass production. Toshio wanted to use relays like those employed in the telephone exchange equipment of those days, in order to make a completely electric calculator.

Computers using relays had already appeared by the late 1950s but they were so large that they required a whole room to themselves, complete with air purification systems. However relays had numerous problems and were easily affected by fine particles and dust. In order to solve this problem, the four Kashio brothers worked to reduce the number of relays from the several thousand (sometimes over ten thousand) used in the giant computers of the day to just 342, through improvements in the circuit design. They also developed an original new type of relay that was hardly affected by dust.

The greatest feature of the four brothers new invention was the adoption of the ten-key format. The calculators at that time used what was called a “full keypad” with just the numerals 0 to 9 for all the digit places. This newly developed relay-type calculator used only 10 number keys, just like pocket calculators today. A unique design was also adopted for the display. Calculators at that time had three display windows, and when calculating “100 + 200 = 300” the numerals “100,” “200,” and “300” were all displayed at the same time. However, with the relay calculator, the numbers disappeared after the next number was entered, and just the final answer appeared at the end. Today this seems like common sense, but at that time it was a revolutionary new idea, and it required a lot of hard work to get it accepted. With these innovations however, compact calculators were realized, and the office calculator was born.