Character Sets

Every time a character is typed on a keyboard a code number is transmitted to the computer.  The code numbers are stored in binary.  Different sets of codes are available for different types of computer.  PCs use a character set called ASCII, American Standard Code for Information Interchange.  A character set is the group of characters that can be coded.  

The next page shows a version of ASCII that uses 7 bits to code each character.  The biggest number you can have with seven bits is 1111111 in binary (127 in denary). The smallest number you can have with seven bits is 0000000 (0 in denary!).  This means that you can have 128 different characters in the character set (using codes 0 to 127).  

Other character encoding systems include: 

Unicode:  A 16-bit encoding system that has 216 (65,536) different characters in its character set. 

EBCDIC (pronounced eb-sid-ic):  Extended Binary Coded Decimal Interchange Code, an 8-bit encoding system that has 28 (255) different characters in its character set. 


7-bit ASCII Table 

ASCII

DEC

Binary

ASCII

DEC

Binary

ASCII

DEC

Binary

ASCII

DEC

Binary

NULL

000

000 0000

space

032

010 0000

@

064

100 0000

`

096

110 0000

SOH

001

000 0001

!

033

010 0001

A

065

10 00001

a

097

110 0001

STX

002

000 0010

"

034

010 0010

B

066

100 0010

b

098

110 0010

ETX

003

000 0011

#

035

010 0011

C

067

100 0011

c

099

110 0011

EOT

004

000 0100

$

036

010 0100

D

068

100 0100

d

100

110 0100

ENQ

005

000 0101

%

037

010 0101

E

069

100 0101

e

101

110 0101

ACK

006

000 0110

&

038

010 0110

F

070

100 0110

f

102

110 0110

BEL

007

000 0111

'

039

010 0111

G

071

100 0111

g

103

110 0111

BS

008

000 1000

(

040

010 1000

H

072

100 1000

h

104

110 1000

HT

009

000 1001

)

041

010 1001

I

073

100 1001

i

105

110 1001

LF

010

000 1010

*

042

010 1010

J

074

100 1010

j

106

110 1010

VT

011

000 1011

+

043

010 1011

K

075

100 1011

k

107

110 1011

FF

012

000 1100

,

044

010 1100

L

076

100 1100

l

108

110 1100

CR

013

000 1101

-

045

010 1101

M

077

100 1101

m

109

110 1101

SO

014

000 1110

.

046

010 1110

N

078

100 1110

n

110

110 1110

SI

015

000 1111

/

047

010 1111

O

079

100 1111

o

111

110 1111

DLE

016

001 0000

0

048

011 0000

P

080

101 0000

p

112

111 0000

DC1

017

001 0001

1

049

011 0001

Q

081

101 0001

q

113

111 0001

DC2

018

001 0010

2

050

011 0010

R

082

101 0010

r

114

111 0010

DC3

019

001 0011

3

051

011 0011

S

083

101 0011

s

115

111 0011

DC4

020

001 0100

4

052

011 0100

T

084

101 0100

t

116

111 0100

NAK

021

001 0101

5

053

011 0101

U

085

101 0101

u

117

111 0101

SYN

022

001 0110

6

054

011 0110

V

086

101 0110

v

118

111 0110

ETB

023

001 0111

7

055

011 0111

W

087

101 0111

w

119

111 0111

CAN

024

001 1000

8

056

011 1000

X

088

101 1000

x

120

111 1000

EM

025

001 1001

9

057

011 1001

Y

089

101 1001

y

121

111 1001

SUB

026

001 1010

:

058

011 1010

Z

090

101 1010

z

122

111 1010

ESC

027

001 1011

;

059

011 1011

[

091

101 1011

{

123

111 1011

FS

028

001 1100

<

060

011 1100

\

092

101 1100

|

124

111 1100

GS

029

001 1101

=

061

011 1101

]

093

101 1101

}

125

111 1101

RS

030

001 1110

>

062

011 1110

^

094

101 1110

~

126

111 1110

US

031

001 1111

?

063

011 1111

_

095

101 1111

DEL

127

111 1111

The characters are in numerical sequence, ie: if “A” is 65 then “C” must be 67.  

Also, they have an order so you can say that “7”<”9” and that “a”>”A”.