What Does the Multimedia Actually Mean?
Literally, multimedia means two or more media.If the publisher of this book wanted to join the current hype about multimedia, he could advertise the book as using multimedia technology.After all, it contains two media:text and graphics（the figures）. Nevertheless, when most people refer to multimedia, they generally mean the combination of two or more continuous media, that is, media have to be played during some well-defined timed times interval, usually with the users interaction. In practice, the two media are normally audio and video, that is, sound plus moving pictures.
In the multimedia environment, we have graphics and text at the same time, we can also add the photograph, animation, good-quality sound, and full motion video.All of the technologies make computers more interesting and much easier to use. For example,a multimedia program can play a segment of movie: a cat was playing a reel of thread, with mewing… The tableau can a be immediately captured and pasted to a text at the side of a paragraph of words.
CD－ROM
CD－ROM is an optical technology that is used to make compact disks for CD stereo systems; it has now been adapted to store data for computers.CD disk is an optical disc, on which data is recorded as a set of dips in the surface. When a laser beam shines across the dips,the reflected distortion represents the data.Optical disc has a 600 megabyte capacity and are well suited for the computer applications needing the vast storage.The playback effect of optical discs for music is very perfect,no hiss and crackle as with other photo-records.A computer system must have a CD driver that is designed to read the disks and translate the data into a form it can process. CD disks can store huge volumes of data and are very useful for reference material an encyclopedia, for example.However, as the name（read-only memory）implies, CD disks cannot be written on or changed in any way.
