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What is a ASCII Code

ASCII is an acronym for American Standard Code for Information Interchange.

It is a code that uses numbers to represent characters. Each letter is assigned a number between 0 and 127. A upper and lower case character are assigned different numbers. For example the character A is assigned the decimal number 65, while a is assigned decimal 97 as shown below int the ASCII table.

The ASCII code predates the Internet and has been around since the days of teletypes and mechanical printers. ASCII decimal numbers from 0 to 31 represent control codes that are not used that much these days. However if you are playing with communications protocols you will see these control codes in use. The ASCII Control Codes table explains what each of these control codes are.

When is ASCII code used

When a computer sends data the keys you press or the text you send and receive is sent as a bunch of numbers. These numbers represent the characters you typed or generated. Because the range of standard ASCII is 0 to 127 it only requires 7 bits or 1 byte of data. For example to send the string cactus.io as ascii it would translate to 99 97 99 116 117 115 46 105 111. Microprocessors only understand bits and bytes. To it everything is a sequence of bits.

What is the difference between an ASCII code and a HTML code

The original ASCII code only had a range of 128 characters which is very limited in the range of characters. It basically only supports the english character set. You could have used the extended ascii characters which ranged from 128 to 255. Because the ascii code range is 0 to 255 it can fit inside 1 byte of data.

The HTML code is based on the different character sets that can range from a single byte character set such as Latin-1 (ISO-8859-1) or UTF-8 which uses multiple bytes to represent a character. Using a charcter set such as UTF-8 gives us a much larger range of character sets.

When using a web browser the web site we are using would normally specify the character set it is using. For example in a HTML5 web page you might see the string <meta charset="utf-8"> in the page source. This tells the browser that the data being sent utilises the UTF-8 character table.

The HTML code is usually in the format of &#169;. The & tells the browser that it is a HTML code and not part of a string. The # after the & tells the browser that the following is an numerical value of a symbol. The ; is to tell the browser that is the end of the code. In the case of &#169;, this is the html code that represents the copyright symbol ©.

Go to the Resources Toolbox for a range of HTML Code tables

Where would I use ASCII codes or HTML codes

You would use ASCII codes for all normal programming and communications when using your Arduino, Rasperry Pi or whatever platform is in use. The only time you would HTML codes is if you are communicating to a web browser.


ASCII Table

Ascii Hex Symbol
0 0 NUL
1 1 SOH
2 2 STX
3 3 ETX
4 4 EOT
5 5 ENQ
6 6 ACK
7 7 BEL
8 8 BS
9 9 TAB
10 A LF
11 B VT
12 C FF
13 D CR
14 E SO
15 F SI
Ascii Hex Symbol
16 10 DLE
17 11 DC1
18 12 DC2
19 13 DC3
20 14 DC4
21 15 NAK
22 16 SYN
23 17 ETB
24 18 CAN
25 19 EM
26 1A SUB
27 1B ESC
28 1C FS
29 1D GS
30 1E RS
31 1F US
Ascii Hex Symbol
32 20 (Space)
33 21 !
34 22 "
35 23 #
36 24 $
37 25 %
38 26 &
39 27 '
40 28 (
41 29 )
42 2A *
43 2B +
44 2C ,
45 2D -
46 2E .
47 2F /
Ascii Hex Symbol
48 30 0
49 31 1
50 32 2
51 33 3
52 34 4
53 35 5
53 36 6
55 37 7
56 38 8
57 39 9
58 3A :
59 3B ;
60 3C <
61 3D =
62 3E >
63 3F ?
Ascii Hex Symbol
64 40 @
65 41 A
66 42 B
67 43 C
68 44 D
69 45 E
70 46 F
71 47 G
72 48 H
73 49 I
74 4A J
75 4B K
76 4C L
77 4D M
78 4E N
79 4F O
Ascii Hex Symbol
80 50 P
81 51 Q
82 52 R
83 53 S
84 54 T
85 55 U
86 56 V
87 57 W
88 58 X
89 59 Y
90 5A Z
91 5B [
92 5C \
93 5D ]
94 5E ^
95 5F _
Ascii Hex Symbol
96 60 '
97 61 a
98 62 b
99 63 c
100 64 d
101 65 e
102 66 f
103 67 g
104 68 h
105 69 i
106 6A j
107 6B k
108 6C l
109 6D m
110 6E n
111 6F o
Ascii Hex Symbol
112 70 p
113 71 q
114 72 r
115 73 s
116 74 t
117 75 u
118 76 v
119 77 w
120 78 x
121 79 y
122 7A z
123 7B (
124 7C |
125 7D )
126 7E ~
127 7F