ASCII Control Codes in Code 128 Barcodes
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AppNote022
Code 128 barcodes can include ASCII control codes as well as all the standard printable
ASCII characters. A keyboard wedge scanner will read a barcode and transmit characters to
the computer just as though they had been typed at the keyboard. The key codes transmitted
from the keyboard and the wedge scanner are in a format particular to the PC architecture;
they are not standard ASCII codes. Every standard ASCII character has an equivalent key
code, and the keyboard wedge scanner automatically performs the conversion and sends the
appropriate key code.
However, virtually all keyboards include many keys for which there are no ASCII
equivalents: the F1 through F12 function keys, for example. These key codes can be sent
from the keyboard to the computer, but there is no equivalent ASCII character that can be
printed in a Code 128 barcode.
Many keyboard wedge scanners can be configured replace a specific barcode character
with a different keyboard code. Since the keyboard wedge scanner transmits key codes to
the computer, it can send any keyboard character. For example, a scanner could be
configured to FS code (ASCII decimal 28) to an F10 key.
Here is a list of ASCII control codes. The first column lists the equivalent CTRL+key
codes (^ used to indicate holding down the CTRL key):
| Key |
ASCII |
Function |
| ^2 |
00 |
NUL null |
| ^A |
01 |
SOH start of header |
| ^B |
02 |
STX start transmission |
| ^C |
03 |
ETX end transmission |
| ^D |
04 |
EOT end of tape |
| ^E |
05 |
ENQ enquiry |
| ^F |
06 |
ACK acknowledge |
| ^G |
07 |
BEL bell |
| ^H |
08 |
BS backspace |
| ^I |
09 |
HT horizontal tab |
| ^J |
10 |
LF line feed |
| ^K |
11 |
VT vertical tab |
| ^L |
12 |
FF form feed |
| ^M |
13 |
CR carriage return |
| ^N |
14 |
SO shift out |
| ^O |
15 |
SI shift in |
| ^P |
16 |
DLE data link enable |
| ^Q |
17 |
DC1 device control 1 |
| ^R |
18 |
DC2 device control 2 |
| ^S |
19 |
DC3 device control 3 |
| ^T |
20 |
DC4 device control 4 |
| ^U |
21 |
NAK negative acknowledge |
| ^V |
22 |
SYN sync |
| ^W |
23 |
ETB |
| ^X |
24 |
CAN cancel |
| ^Y |
25 |
EM |
| ^Z |
26 |
SUB substitute |
| ^[ |
27 |
ESC escape |
| ^\ |
28 |
FS field separator |
| ^] |
29 |
GS group separator |
| ^6 |
30 |
RS record separator |
| ^- |
31 |
US |
After this comes the space bar (32) followed by the normal printable
characters.
