Character sets

All data is stored inside a computer as numbers. Each character in text is stored as a binary number.

A common way to do this is to use American Standard Code for Information Interchange (ASCII).

This is just a standard for representing letters in binary. For example, 01000001 (65₁₀) is A, 01000010 (66₁₀) is B, etc. The total amount of characters a computer can use is called the character set.

ASCII table

Code	Character	Code	Character	Code	Character	Code	Character
0		32	Space	64	@	96	’
1		33	!	65	A	97	a
2		34	”	66	B	98	b
3		35	#	67	C	99	c
4		36	$	68	D	100	d
5		37	%	69	E	101	e
6		38	&	70	F	102	f
7	Bell	39	’	71	G	103	g
8	Backspace	40	(	72	H	104	h
9		41	)	73	I	105	i
10	New line	42	*	74	J	106	j
11		43	+	75	K	107	k
12	New page	44	,	76	L	108	l
13	Return	45	-	77	M	109	m
14	Shift (in)	46	.	78	N	110	n
15	Shift (out)	47	/	79	O	111	o
16		48	0	80	P	112	p
17		49	1	81	Q	113	q
18		50	2	82	R	114	r
19		51	3	83	S	115	s
20		52	4	84	T	116	t
21		53	5	85	U	117	u
22		54	6	86	V	118	v
23		55	7	87	W	119	w
24		56	8	88	X	120	x
25		57	9	89	Y	121	y
26		58	:	90	Z	122	z
27	Escape	59	;	91	[	123	{
28		60	˂	92	\	124	\|
29		61	=	93	]	125	}
30		62	˃	94	^	126	~
31		63	?	95	_	127	_

Code	0
Character
Code	32
Character	Space
Code	64
Character	@
Code	96
Character	’

Code	1
Character
Code	33
Character	!
Code	65
Character	A
Code	97
Character	a

Code	2
Character
Code	34
Character	”
Code	66
Character	B
Code	98
Character	b

Code	3
Character
Code	35
Character	#
Code	67
Character	C
Code	99
Character	c

Code	4
Character
Code	36
Character	$
Code	68
Character	D
Code	100
Character	d

Code	5
Character
Code	37
Character	%
Code	69
Character	E
Code	101
Character	e

Code	6
Character
Code	38
Character	&
Code	70
Character	F
Code	102
Character	f

Code	7
Character	Bell
Code	39
Character	’
Code	71
Character	G
Code	103
Character	g

Code	8
Character	Backspace
Code	40
Character	(
Code	72
Character	H
Code	104
Character	h

Code	9
Character
Code	41
Character	)
Code	73
Character	I
Code	105
Character	i

Code	10
Character	New line
Code	42
Character	*
Code	74
Character	J
Code	106
Character	j

Code	11
Character
Code	43
Character	+
Code	75
Character	K
Code	107
Character	k

Code	12
Character	New page
Code	44
Character	,
Code	76
Character	L
Code	108
Character	l

Code	13
Character	Return
Code	45
Character	-
Code	77
Character	M
Code	109
Character	m

Code	14
Character	Shift (in)
Code	46
Character	.
Code	78
Character	N
Code	110
Character	n

Code	15
Character	Shift (out)
Code	47
Character	/
Code	79
Character	O
Code	111
Character	o

Code	16
Character
Code	48
Character	0
Code	80
Character	P
Code	112
Character	p

Code	17
Character
Code	49
Character	1
Code	81
Character	Q
Code	113
Character	q

Code	18
Character
Code	50
Character	2
Code	82
Character	R
Code	114
Character	r

Code	19
Character
Code	51
Character	3
Code	83
Character	S
Code	115
Character	s

Code	20
Character
Code	52
Character	4
Code	84
Character	T
Code	116
Character	t

Code	21
Character
Code	53
Character	5
Code	85
Character	U
Code	117
Character	u

Code	22
Character
Code	54
Character	6
Code	86
Character	V
Code	118
Character	v

Code	23
Character
Code	55
Character	7
Code	87
Character	W
Code	119
Character	w

Code	24
Character
Code	56
Character	8
Code	88
Character	X
Code	120
Character	x

Code	25
Character
Code	57
Character	9
Code	89
Character	Y
Code	121
Character	y

Code	26
Character
Code	58
Character	:
Code	90
Character	Z
Code	122
Character	z

Code	27
Character	Escape
Code	59
Character	;
Code	91
Character	[
Code	123
Character	{

Code	28
Character
Code	60
Character	˂
Code	92
Character	\
Code	124
Character	\|

Code	29
Character
Code	61
Character	=
Code	93
Character	]
Code	125
Character	}

Code	30
Character
Code	62
Character	˃
Code	94
Character	^
Code	126
Character	~

Code	31
Character
Code	63
Character	?
Code	95
Character	_
Code	127
Character	_

7-bit ASCII

Bytes are frequently used to hold individual characters in a text document. In the character set, each binary value between 0 and 127 is given a specific character. This means we have a total of 128 different characters (remember we begin at 0).

8-bit (extended) ASCII

Most computers extend the ASCII character set to use the full range of 256 characters available in a byte. The upper 128 characters handle special things like accented characters from common foreign languages, or symbols such as é or ©.

Unicode

Some languages use a completely different alphabet to the English language alphabet. It would be impossible to use ASCII (7 bit) or Extended ASCII (8bit) to create all the additional characters needed for these alphabets.

Unicode can assign a lot more characters. The 1-byte system used in 8-bit ASCII can only represent up to 256 characters. Unicode uses a 2-byte system for each character, which means that more than 65,000 characters can be represented.

This allows us to represent all the characters needed in languages such as Japanese or Greek, the Cyrillic alphabets or Braille.

Data types

Data type	Description	Example data
Integer	These are whole numbers only	0, 1, 2, 3
Real/Float	These are numbers that can have a decimal part	0.1, 1.2, 3.4, 5.0
Boolean	This has two values only	True/False, 1/0, Y/N
Character	This is a single letter, number or symbol	A, B, C, @, *
String	This is used for text, and can include any character	Digital Technology, aeg54jklM
Date/Time	Used for dates and times	20:55 29/11/2016

Data type	Integer
Description	These are whole numbers only
Example data	0, 1, 2, 3

Data type	Real/Float
Description	These are numbers that can have a decimal part
Example data	0.1, 1.2, 3.4, 5.0

Data type	Boolean
Description	This has two values only
Example data	True/False, 1/0, Y/N

Data type	Character
Description	This is a single letter, number or symbol
Example data	A, B, C, @, *

Data type	String
Description	This is used for text, and can include any character
Example data	Digital Technology, aeg54jklM

Data type	Date/Time
Description	Used for dates and times
Example data	20:55 29/11/2016

Digital data - CCEACharacter sets