Britannica editor Warren Preece had been able to foresee the possibility of an optical disc encyclopedia because of breakthrough engineering developments that had taken place in Europe and Japan. Klass Compaan, a physicist with Philips research, based in The Netherlands, had conceived of the compact disc in 1969 and, with Piet Kramer, had produced the first color videodisc prototype in 1972. Philips then worked with Sony to develop a smaller compact disc standard for just storing audio signals.

The audio compact disc that emerged was made with a polycarbonate substrate, molded with pits that permitted a laser beam to read timing and tracking data. The so-called Red Book format of the compact disc was released in Japan and Europe in 1982, and in the U.S. the following year. A derivative format, designed to hold multimedia information and be played back on a computer was given the unwieldy name Compact Disc- Read Only Memory, CD-ROM for short. This was launched into the nascent personal computer market in 1985, several years after the first prototypes had been shown.

Grolier Publishing quickly put a text-only encyclopedia on a videodisc and also a CD-ROM in 1985. Most early CD-ROMs published were specialized compendia designed for commercial, not consumer, use. Navigation was accomplished through rules-based Boolean text string searches. Discs with sound, pictures, video and animation, although supported by the CD-ROM format, were not available.

Microsoft believed that for sales of its operating system to grow at an exponential rate, software developers needed to be encouraged to use the new CD-ROM storage media to create compelling software for consumers. The assumption was that this would drive consumers to regard PCs in the home not just as gaming facilitators, but as a requirement for their children’s education. To this end, Microsoft showed off a CD-ROM multi-media encyclopedia demonstration disc at a CD-ROM developer’s conference it held in 1986. The dozen five- page articles on the demonstration disc contained text, graphics, sound, a motion sequence and animation.