Kazuo Kashio, one of four brothers who founded Casio Computer, the Japanese company behind G-Shock watches, calculators and other electronics equipment, died June 18 at a Tokyo hospital. He was 89.

The cause was aspiration pneumonia, the company said.

Mr. Kashio, who was chairman of the company and served as president, is credited with making the calculator an everyday product through Casio Mini. He also helped popularize G-Shock, which has grown into an internationally recognized brand since its 1983 debut.

Mr. Kashio succeeded his older brother Tadao, who served as Casio’s second president. The first president was the brothers’ father.

G-Shock still commands a following after 35 years, despite the advent of smartphones and other devices. G-Shock loyalists praise the watches’ durability and accuracy.

Mr. Kashio felt that a company must keep reinventing itself to survive, pursuing “continual change.”

“By breaking free from preconceptions and conventional notions, we have conceived products that are truly needed and used our digital technologies to make them a reality,” he said in one of his messages as chairman. “Products based on new ideas create new markets.”

Mr. Kashio had a reputation for being passionate and tough, said Kazuhiko Ichinose, a company spokesman.

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Mr. Kashio also worked on popularizing the QV-10 digital camera, which went on sale in 1995. It introduced a screen on the back for previewing images, now a standard feature on digital cameras.

A machine shop set up in 1946 by Tadao Kashio evolved into Casio. But Casio had big ambitions, eyeing foreign markets from its early years. It started to export calculators in 1966, and the reception overseas was positive.

Mr. Kashio’s survivors include his wife, Soko Kashio, and three children. His son, Kazuhiro Kashio, is the Casio president.