ASCII (American Standard Code for Information Interchange)

It is well-known for much people that in fact computers only handle 0s (zeros) and 1 (ones). By means of sequences of 0 and 1 the computer can express in binary form diverse ranks of numbers (as explains the document numeral radixes).

Nevertheless there is no such evident way to represent letters with 0s and 1s. Then, to be able to do that, computers use the ASCII code, that is a table or list that contains all the letters in the alphabet plus other additional characters. In this code each character is always represented by the same order number. For example, in ASCII code the capital letter A is always represented by the order number 65, which is easily representable using 0s and 1s in binary (1000001).

The standard ASCII code defines 128 character codes (from 0 to 127), of which, the first 32 are control codes (non-printable), and the other 96 are representable characters:

*

0

1

2

3

4

5

6

7

8

9

A

B

C

D

E

F

0

NUL

SOH

STX

ETX

EOT

ENQ

ACK

BEL

BS

TAB

LF

VT

FF

CR

SO

SI

1

DLE

DC1

DC2

DC3

DC4

NAK

SYN

ETB

CAN

EM

SUB

ESC

FS

GS

RS

US

2

!

"

#

$

%

&

'

(

)

*

+

,

-

.

/

3

0

1

2

3

4

5

6

7

8

9

:

;

<

=

>

?

4

@

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

5

P

Q

R

S

T

U

V

W

X

Y

Z

[

\

]

^

_

6

`

a

b

c

d

e

f

g

h

i

j

k

l

m

n

o

7

p

q

r

s

t

u

v

w

x

y

z

{

|

}

~

* This panel is organized to be easily read in hexadecimal: row numbers represent the first digit and the column numbers represent the second one. For example, the A character is located at the 4throw and the 1st column, for that it would be represented in hexadecimal as 0x41 (65).

In addition to the 128 standard ASCII codes there are other 128 that are known as extended ASCII, and that are platform-dependent. So there is more than one extended ASCII character set.

The two most used extended ASCII character sets are the one known as OEM, that comes from the default character set incorporated by default in the IBM-PC and the other is the ANSI extend ASCII which is used by recent operating systems.

First of them, the OEM character set, is included in the immense majority of PC compatibles when starting before loading any operating system or under MS-DOS system. It includes diverse foreign signs, some marked characters and pieces to represent panels. Unfortunately it is usually redefined according to regional configurations to incorporate own symbols in many countries.

Here you have an interactive Decimal-Hexadecimal-Octal-ASCII converter (Netscape 3+ or MSIE 4+):

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