The CASSIOPEIA was jointly developed by Casio and Microsoft, and was the first handheld PC in the world. It used an operating system called WindowsCE, newly developed for mobile information devices with small memory capacity, and allowed a high level of data exchange with Windows PCs. With an open platform just like a PC, software makers were able to develop a wide array of applications for the device.

With the widespread adoption of Windows95, many written materials, from personal data to office documents, were now being handled by PCs in the workplace. As a result, mobile information terminals became needed to enable access to this data wherever it was needed. CASSIOPEIA was developed to expand the office information revolution brought about by the PC to the personal level.