LARGE capacity optical memories are now being applied in various fields to a variety of products, including magneto-optical discs for calculators, MDs (mini discs), portable personal computers (PCs) and electronic organisers. Sharp Corp in Japan is one of the firms at the forefront of opto-electronic technology development, creating memories for CDs and calculators, including rewritable optical disc memory systems. As the volume, range and availability of information increases, optical memory technology is certain to play a key part. Its advantages are its large capacity, high reliability and high-speed random access. The optical pick-up function uses a semiconductor laser that plays and records discs without touching them. The high-speed random access design of the pick-up function allows it to move quickly when searching for tracks of information. Large capacity, pre-recorded CD-ROMs, for example, can be used like CDs to give users access to dictionaries, or games, via a personal computer. A 12-cm CD-ROM has a huge storage capacity equivalent to 900 paperback books, each of 400 pages in length - a total of 360,000 pages. Memory-orientated products such as MD players, and its challenger for the present analogue market, digital compact cassettes (DCC), are now just arriving on to the Asian market. DCCs, such as MDs, also produce high-quality digital sound, but can also playback analogue cassette tape recordings. The DCC compresses digital signals to one quarter the data amount to record and then expands the same during playback. A fixed-head designed with thin-film technology is used to record and playback information. The DCC operates in nearly the same manner as existing analogue cassette tapes. However, all DCC players have an auto reverse function, so hub holes are only on one side of the tape. Extra information, such as the name of the artist or composer, commentary on the work and text, is also programmed on to pre-recorded software. The debate now is whether people will opt for the faster access of MDs, or the DCCs, which allow them the convenience of using their existing analogue tapes.