Appendix C: ASCII Character Codes

MOST SIGNIFICANT BITS

LEAST SIGNIFICANT BITS

0

1

2

3

4

5

6

7

0

Null

Data Link Escape

Space

0

@

P

`

p

1

Start of Heading

Device Control 1

!

1

A

Q

a

q

2

Start of Text

Device Control 2

2

B

R

b

r

3

End of Text

Device Control 3

#

3

C

S

c

s

4

End of Transmit

Device Control 4

$

4

D

T

d

t

5

Enquiry

Neg Acknowledge

%

5

E

U

e

u

6

Acknowledge

Synchronous Idle

&

6

F

V

f

v

7

Bell

End of Trans Block

7

G

W

g

w

8

Backspace

Cancel

(

8

H

X

h

x

9

Horizontal Tab

End of Medium

)

9

I

Y

i

y

A

Line Feed

Substitute

*

:

J

Z

j

z

B

Vertical Tab

Escape

+

;

K

[

k

{

C

Form Feed

File Separator

,

<

L

\

l

|

D

Carriage Return

Group Separator

-

=

M

]

m

}

E

Shift Out

Record Separator

.

>

N

^

n

~

F

Shift In

Unit Separator

/

?

O

_

o

Delete

The American Standard Code for Information Interchange contains both printable and nonprintable characters, e.g., backspace or line feed. The devices that use ASCII data do not have to implement the entire character set. An LCD panel, for example, probably will not do anything if it receives the control character to ring a bell (0x7). If a device is an ASCII device, then it will only accept ASCII data, and numbers must be sent in their respective ASCII representations. For example, if you want to print a 9, then a printer must receive the value 0x39. Note that the most significant bit of an ASCII value is either zero or a parity bit, depending on how the programmer wants to use it.