A Multimedia Primer   

For journalists, a quick course in Multimedia 101 begins with the rush toward a world where all pictures, sound and words can be "digitized" – expressed in the binary language of computers as a series of "0s" and "1s."

Inside the computer, this language is associated with either the presence or absence of electrical energy. The two possibilities, energy or no energy, correspond to the zeros and ones. Each zero or one is a "bit" of information, and while individual bits can't "say" much, they can be assembled into larger groups that can convey complex information that is organized and interpreted by the computer.

These larger groups of bits are known as "bytes," and advances in computers have allowed them to process ever-increasing sizes of bytes.

Outside the computer, digitizing information means that every dot of color in a photograph can be given a digital home, or address, and its precise shade defined by a number that can be translated on any computer screen as the same hue. The same is true for text and sound. They then can be blended together with relative ease.

Once expressed digitally, information can be shipped at the speed of light and, when using optical fibers, converted into light pulses and reconverted into digital form at its destination. When that information is received, it can be converted into precise images, sounds and text.

Each new generation of computer chips has greatly increased the speed and storage capabilities of computers, making it economically feasible to manipulate, move and store large amounts of digitized information. Even so, the fanciest personal computer would have a hard time downloading and displaying even Walt Disney's 1928 cartoon, "Steamboat Willie," were it not for equally impressive advances in digital "compression" – software that compresses the information needed to convey accurate images.

While better compression programs have been shrinking video transmission files, faster transmission speeds have been introduced to ship these files on their way. The telephone modem, which produces that eardrum-splitting noise you hear when you accidentally pick up a fax or computer line, only a handful of years ago was boasting speeds of 300 bits per second. The newest devices now offer speeds of 28,800 bps, with afterburners that can boost transmission to more than 230,000 bps.

But even such digital hot rods would be of limited value if the information highway were not made wider to accommodate more traffic. In this world, where transmission bandwidth is crucial, fiber optics and other transmission media have created a phenomenon that has been called the "Bandwidth Bonanza." Even plain old copper phone wires are being souped up.

Tele-Communications Inc., the cable TV giant, is rushing to upgrade its systems and bring on the age of 500 cable channels. But even this vast programming environment would be topped by the marriages of cable and telephone technologies now being celebrated, if not yet consummated.

The telephone industry has a marvelous switching system, which is moving quickly to become completely digitized. It allows you to pick up your phone whenever you want and dial just about any other telephone in the world. Now, imagine if those other telephones weren't Aunt Ruthie but individual programming choices such as movies, home shopping and interactive video games, all available on demand, delivered over coaxial cable or glass fiber. The idea of 500 channels suddenly becomes a moot concept, replaced by a world that can produce any one channel – the one you want – on demand. – P.M.