Definition: word

(1) See Microsoft Word.

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

The larger the word, the faster the computer calculates and compares (processes). However, the speed increase also depends on the size of the data being calculated. Given the same clock rate, 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. The 16-bit computer requires additional steps (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 and 64-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. See 32-bit computer and 64-bit computer.

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.)