ARPUS/ce, Version 2.6.2 (03/10/05) (SCCS 1.2)
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NAME
ASCII : American National Standard Code for Information Interchange
DESCRIPTION
Data exchanged between a terminal and a host is generally in a standard
code or representation. ASCII is one such code. Ce is designed as an
ASCII based text editor and uses ASCII as it's internal representation.
Other references to ASCII include USASCII and ANSCII but the standard
acronym is ASCII.
ASCII is the North American version of the International Alphabet No. 5
(IA5)
The ASCII character code was developed by members of ANSI and adopted
as a standard in 1963, based on the character set used in the Teletype
Model 33 teleprinter. This version had no lower case characters. Since
then, two revisions have been made to the original ASCII code, one in
1968, and the second in 1977. The 1977 version of ASCII is in use today.
This version is also known as ANSI X3.4-1977.
ASCII is a seven bit code. This means that all characters are represented
in binary form by a seven bit sequence. A group of seven bits represents
a total of 128 combinations. ASCII defines all 128 combinations, consisting
of 33 control characters, 52 alphabetic characters, 10 numeric characters,
and 33 symbols.
There are some who claim that ASCII is an eight bit code. This comes
about because many systems append an additional bit to the end of each
ASCII character. This optional bit is called a parity bit and is used
for detecting errors. ASCII characters are only seven bits in length
but may be surrounded by other overhead bits.
The ASCII binary or hex code is obtained by starting with the column
followed by the row. For example, the character A is hex 41 or
binary 1000001.
=================================================================
| Binary 000 001 010 011 100 101 110 111 |
| -------------------------------------------------------
| | HEX 0 1 2 3 4 5 6 7 |
| | -------------------------------------------------
| 0000 | 0 | NUL | DLE | SP | 0 | @ | P | ` | p |
| | -------------------------------------------------
| 0001 | 1 | SOH | DC1 | ! | 1 | A | Q | a | q |
| | -------------------------------------------------
| 0010 | 2 | STX | DC2 | " | 2 | B | R | b | r |
| | -------------------------------------------------
| 0011 | 3 | ETX | DC3 | # | 3 | C | S | c | s |
| | -------------------------------------------------
| 0100 | 4 | EOT | DC4 | $ | 4 | D | T | d | t |
| | -------------------------------------------------
| 0101 | 5 | ENQ | NAK | % | 5 | E | U | e | u |
| | -------------------------------------------------
| 0110 | 6 | ACK | SYN | & | 6 | F | V | f | v |
| | -------------------------------------------------
| 0111 | 7 | BEL | ETB | ' | 7 | G | W | g | w |
| | -------------------------------------------------
| 1000 | 8 | BS | CAN | ( | 8 | H | X | h | x |
| | -------------------------------------------------
| 1001 | 9 | HT | EM | ) | 9 | I | Y | i | y |
| | -------------------------------------------------
| 1010 | A | LF | SUB | * | : | J | Z | j | z |
| | -------------------------------------------------
| 1011 | B | VT | ESC | + | ; | K | [ | k | { |
| | -------------------------------------------------
| 1100 | C | FF | FS | , | < | L | \ | l | | |
| | -------------------------------------------------
| 1101 | D | CR | GS | - | = | M | ] | m | } |
| | -------------------------------------------------
| 1110 | E | SO | RS | . | > | N | ^ | n | ~ |
| | -------------------------------------------------
| 1111 | F | SI | US | / | ? | O | _ | o | DEL |
=================================================================
NOTES
The first two columns of the ASCII chart contain control characters.
These are characters which cause actions or functions to be performed
rather than causing printing to occur.
The CTRL key on keyboards maps columns 4, 5 into columns 0, 1
respectively. For example :
CTRL-G = BEL (bell)
CTRL-U = NAK (Negative AcKnowledgement)
CTRL-H = BS (BackSpace)
CTRL-Q = DC1 (XON)
CTRL-S = DC3 (XOFF)
HEX 27 is the single quote character (')
HEX 60 is the tic character (`)
NUL
- Hex 00
- the Null character
- A control character used for media fill or time fill.
- Null characters may be inserted into or removed from a stream of
data without affecting the information content of that stream.
SOH
- Hex 01
- Start Of Heading
- A communication control (CC) character used as the first character
of a heading of a data block.
STX
- Hex 02
- Start of TeXt
- A communication control (CC) character that precedes a text field.
ETX
- Hex 03
- End of TeXt
- A communication control (CC) character that terminates a text field.
EOT
- Hex 04
- End Of Transmission
- A communication control (CC) character used to indicate the conclusion
of a transmission sequence. In some protocols, like IBM BSC, this
character is used by the control station to stop remote stations from
sending.
ENQ
- Hex 05
- ENQuiry
- A communication control (CC) character used to request a response
from another station. In Stop-and-Wait ARQ, the station receiving
the ENQ would respond with a retransmission of the previous data
block.
ACK
- Hex 06
- ACKnowledge
- A communication control (CC) character transmitted by a receiver
as an affirmative response to a sender.
BEL
- Hex 07
- Bell
- A control character normally used to call attention. A terminal would
emit a sound from its speaker when it receives a BEL character. Note
that the ASCII standard considers BEL a character that has general
purpose usage meaning that it can be used by a vendor for an unusual
function.
BS
- Hex 08
- BackSpace
- A format effector (FE) which causes movement backward by one position
on the same line.
HT
- Hex 09
- Horizontal Tabulation
- A format effector (FE) which causes movement forward to the next
predefined position on the same line.
LF
- Hex 0A
- Line Feed
- A format effector (FE) that causes movement down to the next line.
This character may also cause movement to the first character
position of the next line. The line feed is optionally referred to
as New Line (NL).
VT
- Hex 0B
- Vertical Tabulation
- A format effector (FE) that causes movement up to the next predetermined
line.
FF
- Hex 0C
- Form Feed
- A format effector (FE) which causes movement to the top of the next page
or form.
CR
- Hex 0D
- Carriage Return
- A format effector (FE) which causes movement to the first character
position on the same line. This character is often used as an End-of-Line
terminator as well.
SO
- Hex 0E
- Shift Out
- A control character that is used in conjunction with SI to extend the
character set. This is accomplished by substituting different graphics
characters for those listed in columns 2 through 7 of the ASCII chart.
SI
- Hex 0F
- Shift In
- A control character used to restore the graphics characters which were
affected by SO (Shift Out).
DLE
- Hex 10
- Data Link Escape
- A communication control (CC) character used for code extension
exclusively to provide supplemental data transmission control
sequences. Code extension takes place when DLE is followed by
a predetermined character or characters.
DC1-4
- Hex 11 (DC1), Hex 12 (DC2), Hex 13 (DC3), Hex 14 (DC4)
- Device Control 1-4
- These four control characters are used to control ancillary devices
connected to data processing devices or telecommunications systems.
Generally they are used to switch devices on or off. Although the
use of these characters is system or device specific, DC1 and DC3
have pseudo-standard usage. These two characters are often used
for data flow control and are known also as XON (DC1) and XOFF
(DC3). Flow control allows a receive to throttle the sender.
- Flow control is typically used by a receiver to temporarily stop
a sender from sending characters. A slow printer connected to a
host is such a situation. If the host sends characters to the
printer at a rate which is too fast for the printer to keep up
with, the printer can stop the host from sending temporarily by
sending an XOFF (ASCII DC3) character to the host. When the printer
is available to receive more data, the printer will send an XON
(ASCII DC1) character to the host.
- Flow control is also used when a user wants to stop the screen
from scrolling so that the screen can be read. XOFF will hold
the screen and is sent from the ASCII keyboard by holding down
the CTRL key and pressing the S key. XON will scroll the screen
and is sent from the ASCII keyboard by holding down the CTRL
key and pressing the Q key.
NAK
- Hex 15
- Negative AcKnowledge
- A communication control (CC) character transmitted by a receiver
as a negative response to the sender.
SYN
- Hex 16
- SYNchronous idle
- A communication control (CC) character used by a synchronous
transmission system for achieving or maintaining synchronism.
ETB
- Hex 17
- End of Transmission Block
- A communication control (CC) character used to indicate the end
of a block of data. Generally, the implication of ETB is there
are more blocks following.
CAN
- Hex 18
- Cancel
- A control character used to indicate that data is in error and/or
should be discarded. The specific meaning of CAN is defined by
each specific application.
EM
- Hex 19
- End of Medium
- A control character used to identify the end of a medium. This
is probably the least used ASCII control character.
SUB
- Hex 1A
- SUBstitute
- A control character which can substitute for a character which
is invalid or received in error.
ESC
- Hex 1B
- ESCape
- A control character intended to provide supplementary characters
(code extension). This is a more general purpose version of the
DLE character.
FS
- Hex 1C
- Field Separator
- An information separator (IS) character whose usage is dependent
on the application.
GS
- Hex 1D
- Group Separator
- An information separator (IS) character whose usage is dependent
on the application.
RS
- Hex 1E
- Record Separator
- An information separator (IS) character whose usage is dependent
on the application.
US
- Hex 1F
- Unit Separator
- An information separator (IS) character whose usage is dependent
on the application.
SP
- Hex 20
- Space character
DEL
- Hex 7F
- DELete
- A control character used primarily to erase or obliterate an
erroneous or unwanted character in punched tape. The character
is also called RUBOUT. DEL may be used the same as NUL. Its use
is application or system specific.
SEE ALSO
EBCDIC : IBM's Extended Binary-Coded Decimal Interchange Code
RELATED HELP FILES:
EBCDIC (Mainframe Code Page)
regexpCon (regular expression)
support (customer support)
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Copyright (c) 2005, Robert Styma Consulting. All rights reserved.
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