ASCII

ASCII ( American Standard Code For Information InterchangeAmerican standard the code for the exchange ; in English is pronounced [e?ski], in Russian it is pronounced [a?ski], and word ASCII more frequently is used in the female kind) - 7 the coding for the idea , of decimal digits, some punctuation marks, arithmetic operations and the managers of the symbols. In the honor of code ASCII even it was named small - "3568 ASCII" (is opened in to year, name obtained more lately).

Content

History ASCII

The first version ASCII was intended in essence for the transfer of communications along the teleprinter. It was developed to year in the firm Bell Laboratories for the change by that created in to year to the 5- bit coding Baudot. (predecessor Baudot she was the Morse code.) in this version yet there were no lower-case letters. They were added in 1967, together with the replacement of pointer to the left to podcherk (_), and pointer upward - to the symbol ^. Thus arose version ASCII, utilized and until now.

In comparison with Baudot, coding ASCII presented the wide collection of usual and managers of symbols, furthermore, letter dispatch contract, also, alphabetically, which made it possible to easily sort texts.

the 7- bit code proved to be convenient for the use also in the computers, since the computers operated with the 8- bit , and the eighth bit could be used for the checking of the parity. (systems, which did not use the checking of parity, made elder bit zero or rarely single.) Semibitnost' made it possible to also add excess 128 symbols for, for example, the support of national alphabets.

Competitor ASCII was the coding EBCDIC, developed in to year by the firm for its operating system System/360. Coding EBCDIC, however, was made under the perforators of those days and possessed the number of the deficiencies: it was 8- bit (consequently, made it possible neither to achieve control of parity nor to add new symbols); letters dispatch although alphabetically, not contract (for example, after I it follows not J, but the symbol of transfer (soft hyphen)). As a result almost everywhere was used ASCII, and EBCDIC - only in system System/360 and compatible with it (for example, WASPS THE EUROPEAN UNION). Now even computers IBM Mainframe they use EBCDIC only for the reverse compatability.

For coding of national symbols was used the mode switch with the aid of symbols SO (Shift Out) and SI (Shift In) - for example, in KOI-". It subsequently proved to be to more conveniently use the 8- bit codings, where lower half of the code table (0 - 127) they occupy symbols ASCII, and upper (128 - 255) - other different necessary symbols.

In of the first 128 symbols also coincide with the appropriate symbols ASCII.

Coding

.0 .1 .2 .3 .4 .5 .6 .7 .8 .9 .A .B .C .D .E .F
0. NUL SOH STX ETX EOT ENQ ACK BEL BS TAB LF VT FF CR SO SI
1. DLE DC1 DC2 DC3 DC4 NAK SYN ETB CAN EM SUB ESC FS GS RS US
2. ! " # $ % & ' ( ) * + , - . /
3. 0 1 2 3 4 5 6 7 8 9 : ; &.lt; = &.gt; ?
4. @ A B C D E F G H I J K L M N O
5. P Q R S T U V W X Y Z [ \ ] ^ _
6. ` a b c d e f g h i j k l m n o
7. p q R s t u v w x y z { | } ~ DEL

Controlling symbols

After the name each symbol is indicated its hexadecimal code.

  1. NUL, 00 - Null, empty. It was always ignored. On punched tapes 1 it was seemed hole, to 0 - absence of hole. Therefore the empty parts of the punched tape prior to the beginning and after the end of the communication consisted of such symbols. Now it is used in many languages of programming as the end of the line. (line is understood as the sequence of symbols.) in some operating systems NUL - the last symbol of any text file.
  2. SOH, 01 - Start Of Heading, the beginning of title.
  3. STX, 02 - Start of Text, the beginning of text. The part of the communication, intended for the press, was called text. Address, check sum t.d. they entered either into the title or into the part of the communication after text.
  4. ETX, 03 - End of Text, the end of the text. Here teleprinter ceased to print. The use of symbol Ctrl- h, which has code 03, for the curtailment of the work of something (usually program), goes back even to those times.
  5. EOT, 04 - End of Transmission, closedown. In system UNIX Ctrl- D, the same having code, indicates the end of the file with the keyboard entry.
  6. ENQ, 05 - Enquire. I please confirmation.
  7. ACK, 06 - Acknowledgement. I confirm.
  8. BEL, 07 - Bell, bell. Now also it is used.
  9. BS, 08 - Backspace, recovery to one symbol. The previous symbol now erases.
  10. TAB, 09 - Tabulation. Was designated also HT - Horizontal Tabulation, horizontal tabulation. In many languages of programming is designated \.t.
  11. LF, 0A - Line Feed, the transfer of line. Now at the end of each line of text file it is placed either this symbol or symbols CR and LF, depending on operating system. In many languages of programming is designated \.n and with the conclusion of text it leads to the transfer of line.
  12. VT, 0B - Vertical Tab, vertical tabulation.
  13. FF, 0C - Form Feed, new page.
  14. CR, 0D - Carriage Return, carriage return. In many languages of programming this symbol, designated \.r, can be used for the recovery into the beginning of line without the transfer of line. In some operating systems the same symbol, designated by Ctrl- M, is placed at the end of each line of the text file before LF.
  15. SO, 0E - Shift Out, change the color of tape (it was used for the dichroic tapes; color changed usually by the red). Subsequently designated the beginning of the use of national coding.
  16. SI, 0F - Shift In, conversely to Shift Out.
  17. DLE, 10 - Data Link Escape, the following symbols make special sense.
  18. DC1, 11 - Device Control 1, the 1st symbol of control of device - to include the device of reading punched tape.
  19. DC2, 12 - Device Control 2, 2-1 symbols of control of device - to include perforator.
  20. DC3, 13 - Device Control 3, the 3rd symbol of control of device - to turn off the device of reading punched tape.
  21. DC4, 14 - Device Control 4, the 4th symbol of control of device - to turn off perforator.
  22. NAK, 15 - Negative Acknowledgment, I do not confirm. Conversely to Acknowledgment.
  23. SYN, 16 - Synchronization. This symbol was transferred, when for the synchronization it was necessary anything to transmit.
  24. ETB, 17 - End of Text Block, the end of the text block. Sometimes text for the technical reasons was divided into the blocks.
  25. CAN, 18 - Cancel, the cancellation (that which was transmitted it is earlier).
  26. EM, 19 - End of Medium, ended punched tape and t.d.
  27. SUB, 1A - Substitute, to substitute. Following symbol - another color or from the additional collection of symbols. Now Ctrl- Z is used as the end of the file with the keyboard entry into systems DOS and Windows. This function does not have any obvious connection with symbol SUB.
  28. ESC, 1B - Escape. Following symbols - something special.
  29. FS, 1C - File Separator, the separator of files.
  30. GS, 1D - Group Separator, the separator of groups.
  31. RS, 1E - Record Separator, the separator of records.
  32. US, 1F - Unit Separator, the separator of yunitov. I.e., were supported 4 levels of the structurization of the data: communication could consist of files, files from the groups, the group of the records, the record from yunitov.
  33. DEL, 7F - Delete, to erase (last symbol). On the punched tapes 1 it was seemed hole, to 0 - absence of hole. Therefore by symbol DEL, which consists of the binary code of all units, it was possible to drive in any symbol. Devices and programs ignored DEL just as NUL.

Cm. also Controlling symbols.

Cm. also

References


 

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