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 ©.

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