ASCII

The American Standard Code for Information Interchange (ASCII) is a 7-bit character-encoding scheme for the Western lower- and uppercase letters (letters without accents only), digits, and punctuation marks. In addition it defines 33 control characters (see Table 1), many of which are obsolete. In total ASCII has space for 2^7 = 128 codes. The ASCII codes from 32 to 126 represent printable characters in binary form (see Table 2), such as are used in computers, telecommunication equipment, and other electronic and mechanical devices. The last ASCII code (127) is DEL(ete) (111 1111) that, being in the last position, has all bits up. Although a control character, it is last in the ASCII table for the historic reason that it enabled the rubout of an incorrect 7-bit paper-tape character (7 holes in the tape) without requiring a complete copy of the tape.

Historically, ASCII developed from telegraph codes. Work on the ASCII standard formally began on October 6, 1960, with the first meeting of the American Standards Association's (ASA) X3.2 subcommittee. The first edition of the standard was published in 1963, ^[1] a major revision (1967) included the the lowercase letters,^[2] and the most recent update was in 1986.^[3]

The order of the printable characters in ASCII is such that alphabetic sorting coincides to a large extent with numeric sorting.

As stated, many of the control characters are obsolete. However, ASCII 9 (tab stop), ASCII 10 (line feed), and ASCII 13 (carriage return) are still in common use. The tab character has the same function as on typewriters and lets the cursor jump from tab stop to tab stop. The pair ASCII 13 and ASCII 10 is used under MS-Windows to indicate end of line ("hard return"), whereas under Unix type operating systems only linefeed (ASCII 10) is used to give a hard return.

Later encoding standards, such as ISO 8859, ANSI 1252 and Unicode UTF-8, are compatible with ASCII, that is, their codes for the first 128 characters are identical to the ASCII codes.

Table 1. Control characters in ASCII

Dec	Hex	Binary	Abbr	Description
0	00	000 0000	NUL	Null character
1	01	000 0001	SOH	Start of Header
2	02	000 0010	STX	Start of Text
3	03	000 0011	ETX	End of Text
4	04	000 0100	EOT	End of Transmission
5	05	000 0101	ENQ	Enquiry
6	06	000 0110	ACK	Acknowledgment
7	07	000 0111	BEL	Bell
8	08	000 1000	BS	Backspace
9	09	000 1001	HT	Horizontal Tab
10	0A	000 1010	LF	Line feed
11	0B	000 1011	VT	Vertical Tab
12	0C	000 1100	FF	Form feed
13	0D	000 1101	CR	Carriage return
14	0E	000 1110	SO	Shift Out
15	0F	000 1111	SI	Shift In
16	10	001 0000	DLE	Data Link Escape
17	11	001 0001	DC1	Device Control 1
18	12	001 0010	DC2	Device Control 2
19	13	001 0011	DC3	Device Control 3
20	14	001 0100	DC4	Device Control 4
21	15	001 0101	NAK	Negative Acknowledgement
22	16	001 0110	SYN	Synchronous idle
23	17	001 0111	ETB	End of Transmission Block
24	18	001 1000	CAN	Cancel
25	19	001 1001	EM	End of Medium
26	1A	001 1010	SUB	Substitute
27	1B	001 1011	ESC	Escape
28	1C	001 1100	FS	File Separator
29	1D	001 1101	GS	Group Separator
30	1E	001 1110	RS	Record Separator
31	1F	001 1111	US	Unit Separator
127	7F	111 1111	DEL	Delete

Table 2. Printable characters in ASCII

Dec Hex Binary Glyph 32 20 010 0000 SP 33 21 010 0001  ! 34 22 010 0010 " 35 23 010 0011 # 36 24 010 0100 $ 37 25 010 0101  % 38 26 010 0110 & 39 27 010 0111 ' 40 28 010 1000 ( 41 29 010 1001 ) 42 2A 010 1010 * 43 2B 010 1011 + 44 2C 010 1100 , 45 2D 010 1101 - 46 2E 010 1110 . 47 2F 010 1111 / 48 30 011 0000 0 49 31 011 0001 1 50 32 011 0010 2 51 33 011 0011 3 52 34 011 0100 4 53 35 011 0101 5 54 36 011 0110 6 55 37 011 0111 7 56 38 011 1000 8 57 39 011 1001 9 58 3A 011 1010  : 59 3B 011 1011  ; 60 3C 011 1100 < 61 3D 011 1101 = 62 3E 011 1110 > 63 3F 011 1111  ?

Dec Hex Binary Glyph 64 40 100 0000 @ 65 41 100 0001 A 66 42 100 0010 B 67 43 100 0011 C 68 44 100 0100 D 69 45 100 0101 E 70 46 100 0110 F 71 47 100 0111 G 72 48 100 1000 H 73 49 100 1001 I 74 4A 100 1010 J 75 4B 100 1011 K 76 4C 100 1100 L 77 4D 100 1101 M 78 4E 100 1110 N 79 4F 100 1111 O 80 50 101 0000 P 81 51 101 0001 Q 82 52 101 0010 R 83 53 101 0011 S 84 54 101 0100 T 85 55 101 0101 U 86 56 101 0110 V 87 57 101 0111 W 88 58 101 1000 X 89 59 101 1001 Y 90 5A 101 1010 Z 91 5B 101 1011 [ 92 5C 101 1100 \ 93 5D 101 1101 ] 94 5E 101 1110 ^ 95 5F 101 1111 _

Dec Hex Binary Glyph 96 60 110 0000 ` 97 61 110 0001 a 98 62 110 0010 b 99 63 110 0011 c 100 64 110 0100 d 101 65 110 0101 e 102 66 110 0110 f 103 67 110 0111 g 104 68 110 1000 h 105 69 110 1001 i 106 6A 110 1010 j 107 6B 110 1011 k 108 6C 110 1100 l 109 6D 110 1101 m 110 6E 110 1110 n 111 6F 110 1111 o 112 70 111 0000 p 113 71 111 0001 q 114 72 111 0010 r 115 73 111 0011 s 116 74 111 0100 t 117 75 111 0101 u 118 76 111 0110 v 119 77 111 0111 w 120 78 111 1000 x 121 79 111 1001 y 122 7A 111 1010 z 123 7B 111 1011 { 124 7C 111 1100 | 125 7D 111 1101 } 126 7E 111 1110 ~

[edit] References

1. ↑ American Standard Code for Information Interchange, ASA X3.4-1963, American Standards Association, June 17, 1963. Copy of text
2. ↑ USA Standard Code for Information Interchange, ANSI X3.4-1967, United States of America Standards Institute, July 7, 1967 Review of 1967 revision
3. ↑ American National Standard for Information Systems — Coded Character Sets — 7-Bit American National Standard Code for Information Interchange (7-Bit ASCII), ANSI X3.4-1986, American National Standards Institute, Inc., March 26, 1986