Editing Integer (computer science) (section)

=== Words ===
{{Main article|Word (computer architecture)}}
The term 'word' is used for a small group of bits that are handled simultaneously by processors of a particular [[computer architecture|architecture]]. The size of a word is thus CPU-specific. Many different word sizes have been used, including 6-, 8-, 12-, 16-, 18-, 24-, 32-, 36-, 39-, 40-, 48-, 60-, and 64-bit. Since it is architectural, the size of a ''word'' is usually set by the first CPU in a family, rather than the characteristics of a later compatible CPU. The meanings of terms derived from ''word'', such as ''longword'', ''doubleword'', ''quadword'', and ''halfword'', also vary with the CPU and OS.<ref name="agnerfog" />

Practically all new desktop processors are capable of using 64-bit words, though [[Embedded system|embedded processors]] with 8- and 16-bit word size are still common. The [[36-bit word length]] was common in the early days of computers.

One important cause of non-portability of software is the incorrect assumption that all computers have the same word size as the computer used by the programmer. For example, if a programmer using the C language incorrectly declares as {{mono|int}} a variable that will be used to store values greater than 2<sup>15</sup>−1, the program will fail on computers with 16-bit integers. That variable should have been declared as {{mono|long}}, which has at least 32 bits on any computer. Programmers may also incorrectly assume that a pointer can be converted to an integer without loss of information, which may work on (some) 32-bit computers, but fail on 64-bit computers with 64-bit pointers and 32-bit integers. This issue is resolved by C99 in [[stdint.h]] in the form of {{code|intptr_t}}.

The ''bitness'' of a program may refer to the word size (or bitness) of the processor on which it runs, or it may refer to the width of a memory address or pointer, which can differ between execution modes or contexts. For example, 64-bit versions of [[Microsoft Windows]] support existing 32-bit binaries, and programs compiled for Linux's [[x32 ABI]] run in 64-bit mode yet use 32-bit memory addresses.<ref>{{cite news |author=Thorsten Leemhuis |date=2011-09-13 |title=Kernel Log: x32 ABI gets around 64-bit drawbacks |url=http://www.h-online.com/open/features/Kernel-Log-x32-ABI-gets-around-64-bit-drawbacks-1342061.html |archive-url=https://web.archive.org/web/20111028081253/http://www.h-online.com/open/features/Kernel-Log-x32-ABI-gets-around-64-bit-drawbacks-1342061.html |archive-date=28 October 2011 |access-date=2011-11-01 |publisher=www.h-online.com}}</ref>