ASCII

ASCII (A merican S tandard C desert for I nformation I nterchange) becomes usually [æski] expenditure-pounds and is an indication coding, those on latin alphabet in largeand lower case is based, as well as numbers, some punctuation marks, how they are necessary in English in the writing, and control characters contains. In many computers and other electronic devices, are represented these represent the text in accordance with ASCII. Further many modern indication codings developed outASCII.

ASCII was published for the first time in the year 1967 and updated last in the year 1986. The indication coding defines, beginning 33 non-printable, today partially redundant indications, which affect the processing of the text, as well as the following 95 printer graphics with the blank:

 ! “#$%&'() *+, -. /0123456789: ; <=>?
@ABCDEFGHIJKLMNOPQRSTUVWXYZ [\] ^_ `abcdefghijklmnopqrstuvwxyz {|} ~

allocation way

ASCII is a quite important of different indication codings, which thatChanges between digital storage and the representation of the characters of the written language make possible.

A bit design from 7 bits is assigned to each indication. There each bit of two values to assume knows gives it <math> to 2^7 = 128 </math> different bit design, alsoas the whole numbers 0-127 to be interpreted can.

In others than the English language used special characters - as for example the German umlauts - can be represented to 7 bit code not all with that; for this 8 to 16 bits was needed. ThoseData processing usually uses 8-bits or a byte as the smallest unit for the data storage. The high order bit in each byte is set on use of the ASCII to the value 0.

already early used computers more than 7 bits, often at least eight-bit number words, - the respected bit can for error correction purposes (parity bit) on the communication lines or for other control problems to be used. Today it is nearly always used however for the extension by ASCII on an 8-bit code. These extensions are to a large extent compatible with the original ASCII, so that all defined indications in the ASCIIalso in the different extensions by the same bit design to be coded. The extensions differ depending upon hard and software and are country-specific.

Composition

the first 32 ASCII character codes (from 00 to 1F) are reserved for control character (control character); see there forthe explanation of the abbreviations in above table. These are indications, which do not represent characters, but serve for the control of such devices (or served), which use ASCII (about printer). Control characters are for example the carriage return for the line-makeup or Bell (thoseBell); their definition is historically justified.

Code 0x20 (FR) is the blank (English. space or brightly), which produces in a text as empty and separator between words used and on the keyboard by the large broad space barbecomes.

The codes 0x21 to 0x7E are contained all printer graphics, both the letters, numbers and punctuation marks (see table).

Code 0x7F (all seven bits set to one) is a special character, which is called “delete symbol” (DEL). ThisCode was used in former times like a control character, around on paper tapes or punch cards an indication already punched later by setting all bits, D. h. by Auslochen of all seven markings, delete to be able - once one does not know existing holes finallycancel again.

No

diacritical indications, which are used in nearly all languages on the basis of latin of alphabet, contain extensions ASCII.

The international standard ISO 646 (1972) was the first attempt to turn on this problem which howeverto compatibility problems led. It is still a seven-bit code and because no other codes were available became some codes in new variants used.

So for instance the ASCII position is 93 for the right angular clammy ones (]) in the German character set variant ISO646-DE by the large U with diaeresis (umlaut) (u) and in the Danish variant ISO 646-DK by large A with ring (Krouzek) (Å) replaced. With programming the square brackets had by the appropriate national Special character to be replaced. This often led to inadvertently amusing results, by for instance the power-up message Apple of the II of “APPLE] [” to “APPLE ÜÄ” mutated.

Different manufacturers developed own eight-bit codes. The code PAGE 437 code mentioned was furthest long timespread, he today still came on the IBM-PC under MS-DOS, and in DOS - or request for input of Ms-Windows, for application.

Even with later standards such as ISO 8859 eight bits were used. Several variants exist, for example ISO 8859-1 for the Western European languages. German-language versions of Ms-Windows (except DOS - windows) use coding Windows-1252 developing on ISO 8859-1 - therefore z see. B. with text files the German umlauts provided under DOS wrongly out, if one it underWindows regards. Many older programs, which used the respected bit for own purposes, could not deal with it. They were often adapted to the new requirements in the course of the time.

In order to become fair the different requirements of the different languages, that became University code (in its character set identically to ISO 10646) develops. It used up to 32 bits per indication and could differentiate thus over four billion different indications. This is limited however to approximately 1 million permitted code values. Thus all can so far by humans used characters to be represented, if they were taken up to the university code standard.UTF-8 is an 8-bit coding of university code, which is downward compatible with ASCII. An indication can take thereby to four 8-bit words. Filter bit variants do not have no moreare used. Nevertheless university code can be coded also by UTF-7 in 7 bits. UTF-8 develops at present (2005) to the uniform standard under most operating systems. Thus among other things some Linux use - distributions UTF-8 according to standard, and ever moreWeb pages are delivered in UTF-8.

ASCII contains only few indications, which are used generally obligatorily for formatting or structuring by text; these come out from the control instructions of the teleprinters. For this count in particular the line feed (LINE feed), the carriage return (carriage return), that horizontal tabulator, the page feed (form feed) and the vertical tabulator. In typical ASCII usually only the carriage return or the line feed is text files, in order to mark the line end beside the printer graphics, whereby in DOS and Windows systems usuallyboth successively to be used, with Apple - and Commodore - computers only the carriage return, on Unix - well-behaved systems only the line feed. The use of further indications to the text formatting is different with different application programs for the text processing. Formatting of text become today alsostrengthens Markup - codes such as z. B. HTML uses.

Compatible indication coding

many indication coding are in such a way sketched the fact that they use 0… 127 the same code for indications within the range as ASCII and for further indications uses the range over 127.

Coding with firmerHere length (selection

) stands a firm number of bytes in each case for an indication. In most coding this is a byte for each indication, with the East Asian writings two or more byte for each indication.

• ISO 8859 with 15 different indication coding for coverall European languages and Thai
• MacRoman, MacCyrillic and other prop. guessing acres of character sets for Apple Mac computer before Mac OS X.
• -代码表窗口 und， z。 B. Windows-1252
• KOI8-R for Russian and KOI8-U for Ukrainian
• ARMSCII for Armenian
• GEOSTD for Georgian
• ISCII for all Indian languages
• TSCII for Tamil
• VISCII for Vietnamesisch
• EUC (Extended UNIX Coding) for several East Asian languages.
• Bend 5 for traditional Chinese (Taiwan, foreign Chinese)
• GB (Guojia Biaozhun) for simplified Chinese (VR China)

to codingwith variable length

around more indications to code to be able, become coded, other indications to become by several bytes with values of over 127 codes the characters 0… 127 in a byte.

• To UTF-8 for university code

see also

• ASCII file
• ASCII table
• kind of ASCII