Editing ASCII (section)

===<span class="anchor" id="8-bit"></span>8-bit codes===
{{Main|Extended ASCII}}{{See also|ISO/IEC 8859|UTF-8}}
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Eventually, as 8-, [[16-bit computing|16-]], and [[32-bit computing|32-bit]] (and later [[64-bit computing|64-bit]]) computers began to replace [[12-bit computing|12-]], [[18-bit computing|18-]], and [[36-bit computing|36-bit]] computers as the norm, it became common to use an 8-bit byte to store each character in memory, providing an opportunity for extended, 8-bit relatives of ASCII. In most cases these developed as true extensions of ASCII, leaving the original character-mapping intact, but adding additional character definitions after the first 128 (i.e., 7-bit) characters. ASCII itself remained a seven-bit code: the term "extended ASCII" has no official status.

For some countries, 8-bit extensions of ASCII were developed that included support for characters used in local languages; for example, [[ISCII]] for India and [[VISCII]] for Vietnam. [[Kaypro]] [[CP/M]] computers used the "upper" 128 characters for the Greek alphabet.{{citation needed|date=November 2023}}

Even for markets where it was not necessary to add many characters to support additional languages, manufacturers of early home computer systems often developed their own 8-bit extensions of ASCII to include additional characters, such as [[box-drawing characters]], [[semigraphics]], and [[Sprite (computer graphics)|video game sprites]]. Often, these additions also replaced control characters (index 0 to 31, as well as index 127) with even more platform-specific extensions. In other cases, the extra bit was used for some other purpose, such as toggling [[inverse video]]; this approach was used by [[ATASCII]], an extension of ASCII developed by [[Atari]].

Most ASCII extensions are based on ASCII-1967 (the current standard), but some extensions are instead based on the earlier ASCII-1963. For example, [[PETSCII]], which was developed by [[Commodore International]] for their [[8-bit computing|8-bit]] systems, is based on ASCII-1963. Likewise, many [[Sharp MZ character set]]s are based on ASCII-1963.

IBM defined [[code page 437]] for the [[IBM PC]], replacing the control characters with graphic symbols such as [[Emoticon|smiley faces]], and mapping additional graphic characters to the upper 128 positions.<ref>{{cite book |url=http://www.bitsavers.org/pdf/ibm/pc/pc/6025008_PC_Technical_Reference_Aug81.pdf |title=Technical Reference |at=Appendix C. Of Characters Keystrokes and Color |edition=First |date=August 1981 |series=Personal Computer Hardware Reference Library |publisher=IBM}}</ref> [[Digital Equipment Corporation]] developed the [[Multinational Character Set]] (DEC-MCS) for use in the popular [[VT220]] [[computer terminal|terminal]] as one of the first extensions designed more for international languages than for block graphics. [[Apple Inc.|Apple]] defined [[Mac OS Roman]] for the Macintosh and [[Adobe Inc.|Adobe]] defined the [[PostScript Standard Encoding]] for [[PostScript]]; both sets contained "international" letters, typographic symbols and punctuation marks instead of graphics, more like modern character sets.

The [[ISO/IEC 8859]] standard (derived from the DEC-MCS) provided a standard that most systems copied (or at least were based on, when not copied exactly). A popular further extension designed by Microsoft, [[Windows-1252]] (often mislabeled as [[ISO-8859-1]]), added the typographic punctuation marks needed for traditional text printing. ISO-8859-1, Windows-1252, and the original 7-bit ASCII were the most common character encoding methods on the [[World Wide Web]] until 2008, when [[UTF-8]] overtook them.<ref name="UTF-8_2008"/>

[[ISO/IEC 4873]] introduced 32 additional control codes defined in the 80–9F [[hexadecimal]] range, as part of extending the 7-bit ASCII encoding to become an 8-bit system.<ref name="Unicode-5.0_2006">{{cite book |author=The Unicode Consortium |editor-first=Julie D. |editor-last=Allen |title=The Unicode standard, Version 5.0 |date=2006-10-27 |publisher=[[Addison-Wesley Professional]] |location=Upper Saddle River, New Jersey, US |isbn=978-0-321-48091-0 |chapter-url=http://unicode.org/book/ch13.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://unicode.org/book/ch13.pdf |archive-date=2022-10-09 |url-status=live |access-date=2015-03-13 |chapter=Chapter 13: Special Areas and Format Characters |page=314}}</ref>