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Definition: word

(1) See Microsoft Word.

(2) The computer's internal storage unit. Word "size" refers to the amount of data a processor's internal data registers can hold and process at one time. Business computers generally have word sizes of 32 or 64 bits. Computers embedded in appliances and consumer products typically have word sizes of 8, 16 or 32 bits. See bit and byte.

Given the same clock rate, the larger the word and the faster the computer calculates and compares. However, the speed increase depends on the size of the data being calculated. Adding a 16-bit number will not be faster in a computer with 32-bit registers than one with 16 bits, but a 24-bit number will be faster. The 16-bit computer requires additional steps to deal with the 24 bits (16 bits first, then the remaining 8), whereas all 24 bits of the number can fit in the 32-bit register. See MHz.

x86 Architecture
In the x86 PC (Intel, AMD, etc.), although the architecture has long supported 32-bit registers, its native word size stems back to its 16-bit origins, and a "single" word is 16 bits. A "double" word is 32 bits.

Many Word Sizes
Since the advent of computers starting in the 1940s, machines have been designed with a variety of word sizes, including 10, 12, 20, 24, 36, 48 and 60 bits.

A 36-Bit Computer
These are 36-bit PDP computers from Digital Equipment Corporation (DEC). In 1971, they were used to send the first email over the Internet (see email for more detail). Both machines barely totaled 500K of memory. (Image courtesy of Dan Murphy, www.opost.com/dlm)