ASCII Code

July 2015

Data coding


Morse code was the first code used for long-distance communication. Samuel F.B. Morse invented it in 1844. This code is made up of dots and dashes (a sort of binary code). It was used to carry out communication much faster than could the Pony Express, the United States mail service at the time. The telegraph operator, who needed a full understanding of the code, was a key figure back then.

Numerous codes were invented, including Émile Baudot's code (known as Baudot code or Murray Code).

On 10 March 1876, Dr Alexander Graham Bell completed the telephone, a revolutionary invention for carrying voice signals over wires. As an interesting aside, the House of Representatives has recently resolved that Antonio Meucci is the inventor of the telephone. Meucci had in fact filed a patent request in 1871, but was unable to continue renewing it past 1874.

These telegraph lines gave rise to teletypewriters, machines which could encode and decode character using Baudot code (the characters were encoded using 5 bits at the time, allowing for only 32 characters).

In the 1960s, ASCII code (for American Standard Code for Information Interchange) was adopted as the new standard. With ASCII, characters can be coded using 8 bits, for 256 possible characters.

What is ASCII code?


Computer memory saves all data in digital form. There is no way to store characters directly. Each character has its digital code equivalent: This is called ASCII code (for American Standard Code for Information Interchange). Basic ASCII code represented characters as 7 bits (for 128 possible characters, numbered from 0 to 127).

  • Codes 0 to 31 are not used for characters They are called control characters, because they are used for actions like:
    • Carriage return (CR)
    • Bell (BEL)
  • Codes 65 to 90 stand for uppercase letters.
  • Codes 97 to 122 stand for lowercase letters

(Changing the 6th bit switches uppercase to lowercase; this is equivalent to adding 32 to the ASCII code in base-10.)

ASCII Character Chart


Character ASCII Code Hexadecimal Code
NUL (Null)000
SOH (Start of heading)101
STX (Start of text)202
ETX (End of text)303
EOT (End of transmission)404
ENQ (Enquiry)505
ACK (Acknowledge)606
BEL (Bell)707
BS (Backspace)808
TAB (Horizontal tabulation)909
LF (Line Feed)100A
VT (Vertical tabulation)110B
FF (Form feed)120C
CR (Carriage return)130D
SO (Shift out)140E
SI (Shift in)150F
DLE (Data link escape)1610
DC1 (Device control 1)1711
DC2 (Device control 2)1812
DC3 (Device control 3)1913
DC4 (Device control 4)2014
NAK (Negative acknowledgement)2115
SYN (Synchronous idle)2216
ETB (End of transmission block)2317
CAN (Cancel)2418
EM (End of medium)2519
SUB (Substitute)261A
ESC (Escape)271B
FS (File separator)281C
GS (Group separator)291D
RS (Record separator)301E
US (Unit separator)311F
SP (Space)3220
!3321
"3422
#3523
$3624
%3725
&3826
'3927
(4028
)4129
*422A
+432B
,442C
-452D
.462E
/472F
04830
14931
25032
35133
45234
55335
65436
75537
85638
95739
:583A
;593B
<603C
=613D
>623E
?633F
@6440
A6541
B6642
C6743
D6844
E6945
F7046
G7147
H7248
I7349
J744A
K754B
L764C
M774D
N784E
O794F
P8050
Q8151
R8252
S8353
T8454
U8555
V8656
W8757
X8858
Y8959
Z905A
[915B
\925C
]935D
^945E
_955F
'9660
a9761
b9862
c9963
d10064
e10165
f10266
g10367
h10468
i10569
j1066A
k1076B
l1086C
m1096D
n1106E
o1116F
p11270
q11371
r11472
s11573
t11674
u11775
v11876
w11977
x12078
y12179
z1227A
{1237B
1247C
}1257D
~1267E
Delete key1277F

Extended ASCII Character Chart


ASCII Code was developed for use with the English language. It does not have accented characters, or language-specific characters. To encode such a character, a different code system is needed. ASCII code was extended to 8 bits (a byte) in order to be able to encode more characters (this is also known as Extended ASCII Code).
This code assigns the values 0 to 255 (coded as 8 bits, i.e. 1 byte) to uppercase and lowercase letters, digits, punctuation marks and other symbols (including accented characters, in the code iso-latin1).

Extended ASCII code is not standardized, and varies depending on which platform is used.




The two most commonly used extended ASCII character sets are:

  • OEM Extended ASCII Code, which was built into the first IBM PCs

OEM Extended ASCII
  • ANSI Extended ASCII CODE, used by recent operating systems

ANSI Extended ASCII

EBCDIC code


EBCDIC code (short for Extended Binary-Coded Decimal Interchange Code), developed by IBM, is used for encoding characters with 8 bits. Though widespread on IBM computers, it has not been as successful as ASCII code.

Unicode


Unicode is a 16-bit character encoding system developed in 1991. Unicode can express any character as a 16-bit code, no matter what operating system or programming language is used.

It includes almost all current alphabets (among them Arabic, Armenian, Cyrillic, Greek, Hebrew, and Latin) and is compatible with ASCII code.

A list of all codes used in Unicode are available at http://www.unicode.org.

For unlimited offline reading, you can download this article for free in PDF format:
Ascii-code .pdf

See also


Código ASCII
Código ASCII
ASCII Code
ASCII Code
Code ASCII
Code ASCII
Codice ASCII
Codice ASCII
O Código ASCII
O Código ASCII
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