KEY CONCEPTS

3-D graphics Not the same as 3-D movies, in which you have a sense of depth. Rather, computer animation, rendered in real time, in which you can infinitely change the viewpoint.

      AVI Abbreviation for audio/video interleave, one of the most common file formats that combines video and sound. 

CD-recordable, CD-R An optical drive that can record music and computer data that, once written to the disk, cannot be erased or changed. 

DVD Abbreviation for digital versatile disk, previously digital video disk. A form of optical storage that uses two layers on each side of a disk to store video and other data.

laser An acronym for light amplification by stimulated emission of radiation, a laser is a device that produces a coherent beam of light. That is, the beam contains one or more extremely pure colors and remains parallel for long distances instead of spreading as light normally does. 

MIDI Acronym for musical instrument digital interface, MIDI is protocol for recording and playing back music on digital synthesizers supported by most sound cares. Rather than representing musical sound directly, it contains information about how music is produced. The resulting sound waves are generated from those already stored in a wave table in the receiving instrument or sound card. 

MPG Acronym for multimedia personal computer and the official definition for a PC that meets the minimum multimedia standards set by the MPC standards group. MPC3 is the current standard for CD-ROM, sound card, and other components. Most PCs today exceed the MPC standard. 

MPEG A term derived from the Motion Pictures Expert Group, MPEG is a specific method of de­compressing video and sound for real-time playback. 

optical drive A storage device that uses a laser to read and write data. 

pit A distorted area on the surface of an optical disk. A pit disperses light from a laser beam aimed the disk so that the drive’s read head does not pick up the beam. 

rewriteable Applied to both compact discs (CD5) and DVD, the term refers to an optical drive or disk on which data can be changed or erased after it is recorded. 

virtual reality The simulation of a real or imagined environment that can be experienced visually in the three dimensions of width, height, and depth and may include other sensory experiences including sound, touch, and feedback from “touched” objects or other forces. 

Wave table synthesis FM synthesis generates sound from digital samples of various musical instruments. FM synthesis works with mathematical descriptions of the sounds rather than the actual recordings. Wave table synthesis is better.

computer’s CD-ROM and DVD drives use small, interchangeable, plastic-encased discs from which data is retrieved using a laser beam, much like compact music discs. And like a music CD, computer CD-ROMs and DVDs store vast amounts of information. This is achieved by using light to record data in a form that’s more tightly packed than the relatively clumsy magnetic read/write heads that a conventional drive must manage. And like music CD players, computer CD-ROM drives are appearing in jukebox con­figurations that automatically change among 6 to 100 CDs as you request different information.

Unlike an audio CD player, however, a CD-ROM drive and a DVD drive installed in a PC is nearly de­void of buttons and LCD readouts, except for a button to load and unload a disc and a light to tell you when the drive is reading a disc. The drive is controlled by software in your PC that sends instructions to controller circuitry that’s either a part of the computer’s motherboard or on a separate board installed in an expansion slot. Together, the software and circuitry manipulate high-tech components that make con­ventional drives seem crude in comparison.

The CD-ROMs and DVDs that are most common are, again like music compact discs, read-only. Your PC can’t write your own data or files to these discs; your PC can retrieve only the information that was stamped on the CDs at the factory. The huge capacity and read-only nature of most CD-ROMs makes the discs the perfect medium for storing reams of data that doesn’t need updating, and for distributing large programs. You can easily find CD-ROMs filled with clip art, photographs, encyclopedias, the complete works of Shakespeare, and entire bookshelves of reference material. Finding similar material on DVD is a tougher job.

Although one DVD can hold the equivalent of 13 CDs, with a few exceptions among computer soft­ware, most DVDs are hit movies to which extra scenes, subtitles, and dubbing has been added. For once, the storage capacity far exceeds the needs of most software.

DVD has not yet become a standard PC component as CD-ROM drives have been for a few years. But both are perfect for multimedia systems. which use video and sound files that need the voluminous stor­age the two technologies supply.

Lately, CD and DVD drives have been getting into the writing business. The price has been falling for CD-R (CD-Recordable) drives that can write data to a special type of compact disc. There is, however, a catch: You can’t write to portions of a writeable CD that already have data written to them. You can add to data that was written to the disc in an earlier session, but you can’t delete or change what’s already there.

Drives for rewriteable CD-ROMs (CD-RW), which overcome the immutability of CD-R, and rewrite-able DVDs are quickly dropping in price. One or the other may, at some time in the future, replace the ubiquitous floppy drive. Floppies, CDs, and DVDs are all portable, compact, and cheap. The main differ­ence is storage capacity, and our storage needs long ago outstripped the lowly floppy disk.