Extended ASCII

ExtendedASCII extension8-bit ASCII8-bit extensionsASCIIextended character setsextensions of ASCIIextra-ASCII charactershigh ASCIIIBM Extended ASCII
Extended ASCII (EASCII or high ASCII) character encodings are eight-bit or larger encodings that include the standard seven-bit ASCII characters, plus additional characters.wikipedia
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Code page

codepagecode pagesOEM character set
IBM called such character sets code pages and assigned numbers to both those they themselves invented as well as many invented and used by other manufacturers.
The IBM origin of the numbering scheme is reflected in the fact that the smallest (first) numbers are assigned to variations of IBM's EBCDIC encoding and slightly larger numbers refer to variations of IBM's extended ASCII encoding as used in its PC hardware.

Code page 437

437CP437codepage 437
DOS computers built for the North American market, for example, used code page 437, which included accented characters needed for French, German, and a few other European languages, as well as some graphical line-drawing characters.
It is sometimes referred to as the "OEM font" or "high ASCII", or as "extended ASCII" (one of many mutually incompatible ASCII extensions).

ASCII

US-ASCIIAmerican Standard Code for Information InterchangeASCII code
Extended ASCII (EASCII or high ASCII) character encodings are eight-bit or larger encodings that include the standard seven-bit ASCII characters, plus additional characters.
One could class some of these variations as "ASCII extensions", although some misuse that term to represent all variants, including those that do not preserve ASCII's character-map in the 7-bit range.

EBCDIC

Extended Binary Coded Decimal Interchange Code
EBCDIC ("the other" major 8-bit character code) likewise developed many extended variants (more than 186 EBCDIC codepages) over the decades.
Both of these problems also hindered the adoption of extended ASCII character sets.

HP Roman

HP Roman-8HP Roman-9Roman-8
Hewlett-Packard started to add European characters to their extended 7-bit / 8-bit ASCII character set HP Roman Extension around 1978/1979 for use with their workstations, terminals and printers.
The character set was originally introduced by Hewlett-Packard as extended ASCII 7-bit codepage named HP Roman Extension (also known as code page 1050, CP1050 or ibm-1050 ), which existed at least since 1978.

Mojibake

displayed incorrectlyerroneously doubly-encoded UTF-8garbage characters
Translating between these sets (transcoding) is complex (especially if a character is not in both sets); and was often not done, producing mojibake (semi-readable resulting text, often users learned how to manually decode it).
Then came 8-bit KOI8 encoding that is an ASCII extension which encodes Cyrillic letters only with high-bit set octets corresponding to 7-bit codes from KOI7.

Control character

control codenon-printing charactercontrol codes
One notable way in which ISO character sets differ from code pages is that the character positions 128 to 159, corresponding to ASCII control characters with the high-order bit set, are specifically unused and undefined in the ISO standards, though they had often been used for printable characters in proprietary code pages, a breaking of ISO standards that was almost universal.
Extended ASCII sets defined by ISO 8859 added the codes 128 through 159 as control characters, this was primarily done so that if the high bit was stripped it would not change a printing character to a C0 control code, but there have been some assignments here, in particular NEL.

Multinational Character Set

DEC Multinational Character SetDEC MCS1100
Digital Equipment Corporation (DEC) developed the Multinational Character Set, which had fewer characters but more letter and diacritic combinations.
Such "extended ASCII" sets were common (the National Replacement Character Set provided sets for more than a dozen European languages), but MCS has the distinction of being the ancestor of ECMA-94 in 1985 and ISO 8859-1 in 1987.

PETSCII

ASCIIgraphic characterspseudo graphic characters
Atari and Commodore home computers added many graphic symbols to their non-standard ASCII (Respectively, ATASCII and PETSCII, based on the original ASCII standard of 1963).

Code point

codepointcode pointscharacter codes
ISO/IEC 6937 is not extended ASCII because its code point 0x24 corresponds to the general currency sign rather than to the dollar sign, but otherwise is if you consider the accent+letter pairs to be an extended character followed by the ASCII one.
For example, the character encoding scheme ASCII comprises 128 code points in the range 0 hex to 7F hex, Extended ASCII comprises 256 code points in the range 0 hex to FF hex, and Unicode comprises 1,114,112 code points in the range 0 hex to 10FFFF hex.

Extended Unix Code

EUC-JPEUC-KREUC
UTF-8 is true extended ASCII, as are some Extended Unix Code encodings.

UTF-8

65001Unicode (UTF-8)AL32UTF8
UTF-8 is true extended ASCII, as are some Extended Unix Code encodings.
This encoding was not satisfactory on performance grounds, among other problems, and the biggest problem was probably that it did not have a clear separation between ASCII and non-ASCII: new UTF-1 tools would be backward compatible with ASCII-encoded text, but UTF-1-encoded text could confuse existing code expecting ASCII (or extended ASCII), because it could contain continuation bytes in the range 0x21–0x7E that meant something else in ASCII, e.g., 0x2F for '/', the Unix path directory separator, and this example is reflected in the name and introductory text of its replacement.

Code page 850

CP850850codepage 850
The larger character set made it possible to create documents in a combination of languages such as English and French (though French computers usually use code page 850), but not, for example, in English and Greek (which required code page 737).

Mac OS Roman

MacRomanMac RomanMac-Roman
Apple Computer introduced their own eight-bit extended ASCII codes in Mac OS, such as Mac OS Roman.

ISO/IEC 8859-5

ISO 8859-5ISO-8859-528595
Variations were standardized for other languages as well: ISO 8859-2 for Eastern European languages and ISO 8859-5 for Cyrillic languages, for example.

Unicode

Unicode StandardUnicode Transformation FormatThe Unicode Standard
ISO 8859-1 is the common 8-bit character encoding used by the X Window System, and most Internet standards used it before Unicode.
UTF-8 (originally developed for Plan 9) has become the main storage encoding on most Unix-like operating systems (though others are also used by some libraries) because it is a relatively easy replacement for traditional extended ASCII character sets.

ISO/IEC 8859

ISO 8859ECMA-94ISO-8859
This later became the basis for other character sets such as the Lotus International Character Set (LICS), ECMA-94 and ISO 8859-1.

ISO/IEC 8859-2

ISO 8859-2ISO-8859-2Latin-2
Variations were standardized for other languages as well: ISO 8859-2 for Eastern European languages and ISO 8859-5 for Cyrillic languages, for example.

Windows-1252

CP12521252CP-1252
Microsoft later created code page 1252, a compatible superset of ISO 8859-1 with extra characters in the ISO unused range.

KOI-8

KOI8GOST 13052KOI-8 Cyrillic

Shift JIS

Shift-JISShift JIS-200410001
Shift JIS is not true extended ASCII.

Character encoding

character setComputer encodingsencoding
Extended ASCII (EASCII or high ASCII) character encodings are eight-bit or larger encodings that include the standard seven-bit ASCII characters, plus additional characters.

8-bit

8-bit computereight-bit8
Extended ASCII (EASCII or high ASCII) character encodings are eight-bit or larger encodings that include the standard seven-bit ASCII characters, plus additional characters.

Bit

bitsbinary digitbinary digits
Extended ASCII (EASCII or high ASCII) character encodings are eight-bit or larger encodings that include the standard seven-bit ASCII characters, plus additional characters.

Teleprinter

teletypeteletypewritertelex
ASCII was designed in the 1960s for teleprinters and telegraphy, and some computing.