Word - Revision history

Jnc: Different computer architectures have different word sizes

2025-10-27T11:42:11Z

Different computer architectures have different word sizes

← Older revision		Revision as of 11:42, 27 October 2025
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	In the widest sense, a '''word''' is an ordered group of bits considered together. In computer ~~architecture, a~~ word may denote data processed by the [[Central Processing Unit\|CPU]], an [[instruction]], an [[address]], or the unit by/in which [[main memory]] is accessed. In early and simple computers, these were to a large extent the same width. However, contemporary practice is generally to give each [[byte]] in main memory its own address. Instructions are also now often smaller than the [[arithmetic logic unit\|ALU]] width; [[physical address\|physical]] and [[virtual address]]es are different sizes, etc.		In the widest sense, a '''word''' is an ordered group of bits considered together. Different computer architectures have different word sizes. A word may denote data processed by the [[Central Processing Unit\|CPU]], an [[instruction]], an [[address]], or the unit by/in which [[main memory]] is accessed. In early and simple computers, these were to a large extent the same width. However, contemporary practice is generally to give each [[byte]] in main memory its own address. Instructions are also now often smaller than the [[arithmetic logic unit\|ALU]] width; [[physical address\|physical]] and [[virtual address]]es are different sizes, etc.

	Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size (for reasons of accuracy of physical computations, the principal early [[application]] for computers) on early [[mainframe]]s, such as the [[IBM 704]] and its descendants; the [[Honeywell 6000 series‎‎]]; and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8 family]].		Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size (for reasons of accuracy of physical computations, the principal early [[application]] for computers) on early [[mainframe]]s, such as the [[IBM 704]] and its descendants; the [[Honeywell 6000 series‎‎]]; and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8 family]].

Jnc: Expan discussion somewhat; cover machine 'width' too

2025-10-26T17:24:14Z

Expan discussion somewhat; cover machine 'width' too

← Older revision		Revision as of 17:24, 26 October 2025
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	In the widest sense, a '''word''' is an ordered group of bits considered together. In computer architecture, a word may denote data processed by the [[Central Processing Unit\|CPU]], an instruction, an address, or the unit by which [[main memory]] is accessed. In early and simple computers, these were to a large ~~extend~~ the same width. However, contemporary practice is to give each [[byte]] in main memory its own address~~; instructions~~ are often smaller than the [[ALU]] width; virtual ~~and physical addresses~~ are different ~~size~~, etc.		In the widest sense, a '''word''' is an ordered group of bits considered together. In computer architecture, a word may denote data processed by the [[Central Processing Unit\|CPU]], an [[instruction]], an [[address]], or the unit by/in which [[main memory]] is accessed. In early and simple computers, these were to a large extent the same width. However, contemporary practice is generally to give each [[byte]] in main memory its own address. Instructions are also now often smaller than the [[arithmetic logic unit\|ALU]] width; [[physical address\|physical]] and [[virtual address]]es are different sizes, etc.

	Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8 family]].		Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size (for reasons of accuracy of physical computations, the principal early [[application]] for computers) on early [[mainframe]]s, such as the [[IBM 704]] and its descendants; the [[Honeywell 6000 series‎‎]]; and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8 family]].

			==Computer 'widths'==

			Machines' 'widths' are often considered to be the machine's word-size, but the discussion is complicated, and made even more confusing, because there is no universally accepted standard for what sets a machine's 'width'. Indeed, for most suggested benchmarks, one can find a machine which violates it:

			* [[address space]] ([[KA10]]; 18 bits - 36-bit machine)
			* instruction size ([[Motorola M68000 family]]; 16 bits - 32-bit machine)
			* [[bus]] width ([[Motorola MC68000]]; 16 bits - 32-bit machine)
			* [[arithmetic logic unit\|ALU]] width ([[LSI-11]]; 8 bits - 16-bit machine)

			Thus, the 'word' size is now usually used as the measure of the machine's 'size'.

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	[[Category: Basics]]		[[Category: Basics]]

Larsbrinkhoff: How about this more complex view?

2023-08-11T09:41:50Z

How about this more complex view?

← Older revision		Revision as of 09:41, 11 August 2023
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	A '''word''' is ~~the basic unit~~ of data ~~on which a~~ [[Central Processing Unit\|CPU]] ~~operates; on many machines it is the size of~~ an [[instruction~~]].~~ [[~~Main~~ memory]] ~~addresses used~~ to ~~name words~~, ~~but~~ contemporary ~~practise~~ is to give each [[byte]] in main memory its own address.		In the widest sense, a '''word''' is an ordered group of bits considered together. In computer architecture, a word may denote data processed by the [[Central Processing Unit\|CPU]], an instruction, an address, or the unit by which [[main memory]] is accessed. In early and simple computers, these were to a large extend the same width. However, contemporary practice is to give each [[byte]] in main memory its own address; instructions are often smaller than the [[ALU]] width; virtual and physical addresses are different size, etc.

	Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8 family]].		Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8 family]].

Jnc: fix link

2019-11-22T20:35:15Z

fix link

← Older revision		Revision as of 20:35, 22 November 2019
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	A '''word''' is the basic unit of data on which a [[Central Processing Unit\|CPU]] operates; on many machines it is the size of an [[instruction]]. [[Main memory]] addresses used to name words, but contemporary practise is to give each [[byte]] in main memory its own address.		A '''word''' is the basic unit of data on which a [[Central Processing Unit\|CPU]] operates; on many machines it is the size of an [[instruction]]. [[Main memory]] addresses used to name words, but contemporary practise is to give each [[byte]] in main memory its own address.

	Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8]].		Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8 family]].

	{{semi-stub}}		{{semi-stub}}

	[[Category: Basics]]		[[Category: Basics]]

Jnc: +cat

2018-12-16T16:22:53Z

+cat

← Older revision		Revision as of 16:22, 16 December 2018
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			[[Category: Basics]]

Jnc: Proper cat

2018-10-21T23:09:58Z

Proper cat

← Older revision		Revision as of 23:09, 21 October 2018
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	Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8]].		Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8]].

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Jnc: A start...

2018-04-16T20:38:25Z

A start...

New page

A '''word''' is the basic unit of data on which a [[Central Processing Unit|CPU]] operates; on many machines it is the size of an [[instruction]]. [[Main memory]] addresses used to name words, but contemporary practise is to give each [[byte]] in main memory its own address.

Words are now usually a power-of-two multiple of an 8-bit byte in size, but in early computers, other word sizes were common. 36 bits was a very popular size on early [[mainframe]]s, such as the [[IBM 704]] and its descendants, the [[Honeywell 6000 series‎‎]], and the [[PDP-10]] family. However, small word sizes were common too, e.g. the 12-bit words of the [[PDP-8]].

{{stub}}