A bit (binary digit) is a one or zero (off or on), and 8 bits is a byte. The number of bytes a device can store is its memory, or storage. In 1986 memory was measured in the thousands or tens of thousands (1 kilobyte is roughly 1,000 bytes). In 1991 memory is measured in the millions (1 megabyte is roughly 1 million bytes), or billions (1 gigabyte is roughly 1 billion bytes). By 1996 it will be measured in the trillions (1 terabyte is roughly 1 trillion bytes), or quadrillions (1 petabyte is roughly 1 quadrillion bytes).
One byte usually corresponds to one character: a letter, number, or punctuation mark. On average an English word is about 5 or 6 bytes and a novel is anywhere from 60,000 to 100,000 words. So roughly, a novel is about 1/2 megabyte, a 500-page textbook is about 1 megabyte, and at VHS (Video Home System) quality a 1 hour movie is about 3/4 gigabytes. And these sizes halve when files are compressed. This report contains about 21,500 words and is about 135 kilobytes.
Memory cost is dropping fast. In 1964 128 kilobytes cost a million dollars. Today that much memory is cheaper than the small amount of plastic used on the chip surrounding it. In 1984 1 megabyte was a lot of memory; few people could afford that much memory, and they all worked at large institutions. By 1991, hundreds of thousands of personal computer users had over 8 megabytes of computer storage and 1 or 2 gigabytes of tape or disc storage.
The Panasonic LM-D501W is a rewriteable optical disc that holds 940 megabytes (roughly 1,800 novels); it is about the size of a compact disc and it costs $140. The 3M 8mm D8-112M is a rewritable digital tape that holds 2.3 gigabytes (roughly 4,600 novels); it is about the size of a cassette tape and it costs $18.
In 1990 IBM succeeded in storing 1/8 gigabyte on a 1 inch square magnetic disc. Just 6 years separate the first IBM 1/8-megabyte chip from the first Hitachi 8-megabyte chip; a 64-fold increase--the equivalent of a doubling every year. Some expect terabyte memories within 10 years. Five such memories would hold more text than the human race has ever produced.