This page has computer terms that start with non-alphanumeric characters. For other characters, you may want to see my articles on Character Sets and on Chat Room Shorthand. I will try put the terms in roughly ASCII or Unicode order. The first few are invisible or "control" characters.

Here are a few general notes:

^@
Control at. NULL. Microsoft SQL Server uses ^0.
ASCII: 0 = x0.
^A
Control a. SOH (Start Of Heading), console interrupt.
ASCII: 1 = x1.
^B
Control b. STX (Start of TeXt), maintenance mode on HP.
ASCII: 2 = x2.
^C
Control c. ETX (End of TeXt).
ASCII: 3 = x3.
^D
Control d. EOT (End Of Transmission), not same as ETB.
ASCII: 4 = x4.
^E
Control e. ENQ (ENQuiry, goes with ACK. Old HP flow control.
ASCII: 5 = x5.
^F
Control f. ACK (ACKnowledge), clears ENQ logon hand.
ASCII: 6 = x6.
^G
Control g. BEL (BELl).
ASCII: 7 = x7.
^H
Control h. BS (BackSpace), works on HP.
\b.
Used to indicate an erasure for effect in chat rooms and such. EGs:
  • Dear Fool^H^H^H^HUser:
  • Dear FoolUser:
  • Dear Fool, er, User:

ASCII: 8 = x8.
^I
Control i. HT (Horizontal Tab). The regular tab.
\t.
ASCII: 9 = x9.
^J
Control j. LF (Line Feed) or NL (New Line) or EOL (End Of Line).
Unix EOL (Win EOL is \r\n).
\n.
Unix EOL.
ASCII: 10 = xA.
^K
Control k. VT (Vertical Tab).
\v.
ASCII: 11 = xB.
^L
Control l. NP (New Page, page eject) or FF (Form Feed).
\f.
ASCII: 12 = xC.
^M
Control m. CR (Carriage Return).
Mac EOL (Win EOL is \r\n).
ASCII: 13 = xD.
^N, ..., ^Z, ^[, ^\, ^], ^^, ^_
I don't have time for these but see Character Sets.
ASCII: 14-31 = xE-x1F.
 
Space.
+ or %20 in URLs.
Force a space in HTML with  .
ASCII: 32 = x20.
!
Exclamation Point. Bang.
Denotes factorial. EG: 3! = 1*2*3 = 6.
Logical NOT. EG: !true.
ASCII: 33 =  x21.
!=
Not equal to symbol. Other symbols used include: <> and .
"
Double quote; double quotation mark.
\".
&quot; in HTML and XML.
ASCII: 34 =  x22.
#
Sharp.
Pound.
Number.
In UNIX shell scripts and PERL this denotes a comment.
Indicates a bookmark in URLs,  i.e. a place on a page such as www.fake.com/home.htm#section2.
ASCII: 35 =  x23.
$
Dollar sign.
In regular expressions, this is a metacharacter that means match at the end of the target string.
In many programming languages, a variable that starts with a $ indicates that the variable is a string.
ASCII: 36 =  x24.
%
Percentage.
Often used to denote modulus, i.e. the remainder after division. EG: 9%4 is 1.
In SQL, this denotes a wildcard for one or more characters.
ASCII: 37 =  x25.
%SYSTEM%
A variable that refers to the location of the system files of a computer. In Windows 9X, this is \Win95\System. In Windows NT, this is \Winnt\System32.
&
Ampersand. And.
In UNIX shell scripts this denotes execution in the background.
Often used to denote string concatenation.
&amp; in HTML and XML.
%26.
Denotes parameters in URLs. EG: www.fake.com?x=23&y=71.
ASCII: 38 =  x26.
&&
Logical AND. EG: true && false.
'
Single quote; single quotation mark.
In MS Visual Basic this denotes a comment.
&apos; in HTML and XML. Somehow does not work in some versions of MSIE6.
\'.
ASCII: 39 =  x27.
(
Left parenthesis.
Exclusive end of an interval
ASCII: 40 =  x28.
)
Right parenthesis.
ASCII: 41 =  x29.
*
Asterisk.
Often used to denote multiplication. EG: 10*2 is 20.
Often used to denote a wildcard for one or more characters.
In SQL, this denotes a selection of all the fields in the specified table(s).
In computers, esp. databases, regular expressions, and UML, this denotes cardinality of "many" as in zero or more.
ASCII: 42 =  x2A.
*NIX
UNIX or Linux.
+
Plus sign.
Often used to denote addition. EG: 10+2 is 12.
Often used to denote the sign of a number. EG: +10 v -10.
ASCII: 43 =  x2B.
,
Comma.
ASCII: 44 =  x2C.
-
Hyphen.
Minus sign.
Denotes a parameter for a command in a CLI (command line interface). EG: ping google.com -t.
ASCII: 45 =  x2D.
.
Period.
Full stop.
Dot. As in "Google dot com".
Matches any one character except for \n in regular expressions.
ASCII: 46 =  x2E.
/
Forward slash. Virgule.
Used to separate directories in UNIX and URIs.
Denotes an addition argument for a command or function.
Denotes division. EG: 10/2 is 5.
ASCII: 47 =  x2F.
0
Zero.
ASCII: 48 = x30.
0-based array
An array whose index numbering start with zero. EG: array(0), array(1), ... See also 1-based array.
1
One.
ASCII: 49 = x31.
10BASE-2
Aka thin coaxial cable or thinnet or coax or RG-58 A/U. It is a copper cable coaxially surrounded by insulation, braided copper shielding, and an outer jacket, approximately 1/4 inch thick. Thinnet is very fast, physically medium in size, fairly inexpensive, flexible, and can go up to 185 m per segment (This is nearly 200 m, thus the -2 in 10BASE-2). Each segment can be up to 30 computers. Unlike 10BASE-5 thinnet usually has its transceiver within the NIC. Thinnet also utilizes convenient BNC connectors which can connect segments with repeaters, T connectors, terminators, etc. See also my article on Media.
10BASE-5
Aka thick coaxial cable or thicknet or yellow cable or thick coax or RG-8 or RG-11. The original media for Ethernet networks. It is a copper cable coaxially surrounded by insulation, braided copper shielding, and an outer jacket, approximately 1/2 inch thick. It is not used as often since it is expensive, heavy, and inflexible. However it is well shielded and a segment can be up to 500 m (Thus the -5 in 10BASE-5.). Each end of 10BASE-5 terminates with a transceiver (that usually has a vampire tap) that connects to an AUI cable (Attached Unit Interface) that connects to the NIC (Network Interface Card). See also my article on Media.
10BASE-F
Fiber optic cabling. 10BAS-F is more often used between LANs than within a LAN. Fiber optic cabling consists of threads of glass surrounded by plastic shielding, Kevlar, and an outer jacket. It will typically use an ST fiber optic connector. Instead of sending electrical signals, it sends pulses of light and which are totally unaffected by external electrical fields. Of the 10BASE family of media, fiber optics is the fastest, physically small, the most expensive, and can go up to 100 km. See also my article on Media.
10BASE-T
Aka UTP (Unshielded Twisted-Pair or twisted pair). UTP is even more popular and cheaper than 10BASE-2. It is 4 pairs of insulated, color coded wire inside one outer jacket. Its connector, RJ-45, looks similar to the typical phone connector, RJ-11, which only has 1 to 3 pairs of wires. Each pair is twisted (to cancel out electrical noise) and each pair is also twisted a different number of twists per inch. UTP is fast, physically small, the least expensive, but has a fairly short maximum length of 100 m between computers and hubs (This would have made it 10BASE-1, but go figure.). UTP also comes in grades 1-5,with grade 3 being the recommended minimum for Ethernet. The big difference between coaxial cabling and UTP is that UTP networks need a hub at the center where each computer connects to. The advantage of the hub is that a downed computer does not affect the network as much as it would in a linearly connected coaxial cable network. See also my article on Media.
100BASE-T
100 Mb/s Ethernet. See also my article on Media.
1000BASE-T
Gigabit Ethernet. IEEE Std. 802.3z. IEEE shorthand for the usage of four pairs of CAT-5 balanced copper cabling and a 5-level coding scheme to transfer data at a rate of 1 Gb/s for distances of up to 100 meters. Many companies already use CAT-5 cabling so this is a popular upgrade.1000BASE-T is compatible with existing network protocols (eg IP, IPX, and AppleTalk). See also my article on Media.
1024 x 768
See SVGA.
1-based array
An array whose index numbering start with one. EG: array(1), array(2), ... See also 0-based array.
1GL
First Generation Language. See programming language.
2
Two.
ASCII: 50 = x32.
2B+D line
See also BRI. See also my article on Removable Storage.
2260
See IBM 3270.
23B+D line
See PRI.
2GL
Second Generation Language. See programming language.
3
Three.
ASCII: 51 = x33.
3270
See IBM 3270.
3GL
Third Generation Language. See programming language.
4
Four.
ASCII: 52 = x34.
404 Not Found Error
A common HTTP Status Code indicating that the server was unable to locate the requested item. See also HTTP Status Codes.
5
Five.
ASCII: 53 = x35.
6
Six.
ASCII: 54 = x36.
640 x 200
See CGA.
640 x 350
See EGA.
640 x 480
See VGA.
7
Seven.
ASCII: 55 = x37.
701
IBM's first true computer.
7 x 24
Seven days a week, twenty-four hours a day. Basically around the clock service.
8
Eight.
ASCII: 56 = x38.
800 x 600
See SVGA.
802.2
IEEE standard for dealing with Ethernet's LLC sub layer of the Data Link Layer of the OSI Reference Model.
802.3
IEEE standard for dealing with the Ethernet's Physical and Data Link Layers of the OSI Reference Model. See also my article on OSI.
802.11
IEEE standard for dealing with wireless networks. 1 or 2 Mb/s transmission in the 2.4 GHz band using either FHSS (Frequency Hopping Spread Spectrum) or DSS (Direct Sequence Spread Spectrum). 802.11 and its descendents (802.11a, etc.) are aka WiFi.
802.11a
Up to 54 Mb/s in the 5.5 GHz band. 802.11a uses an OFDM (Orthogonal Frequency Division Multiplexing) encoding scheme rather than FHSS or DSSS.
802.11b
Aka 802.11 High Rate. Up to 11 Mb/s transmission (with a fallback to 5.5, 2 and 1 Mb/s) in the 2.4 GHz band. 802.11b uses DSSS with CCK (Complementary Code Keying).
802.11g
Up to 54 Mb/s in the 2.4 GHz band. Uses DSSS with CCK when below 20 Mib/s. Uses OFDM when above 20 Mib/s.
802.11n
Up to 135-540 Mib/s at 20-40 MHz. This standard should be approved ca. 2007.
9
Nine.
ASCII: 57 = x39.
:
Colon
ASCII: 58 =  x3A.
::=
"is defined as" in BNF notation. Other symbols used include: .
;
Semicolon.
ASCII: 59 =  x3B.
<
Left angle brackets. Left chevron.
Less than symbol. EG: 3 < 4.
&lt; in HTML and XML.
Often used to enclose tags (descriptions of syntactic elements) in SGML, HTML, XML, and such. EG: <head>.
ASCII: 60 =  x3C.
<<
Much less than symbol. EG: 1 << 1000.
<=
Less than or equal to symbol. Other symbols used include: .
< >
Not equal to symbol. Other symbols used include: != and .
Often used to enclose tags (descriptions of syntactic elements) in SGML, HTML, XML, and such. EG: <head>.
=
Equal sign. EG: 5 = 3 + 2. The equal sign was invented in 1557 by Robert Recorde.
Assignment operator. EG: x = 3 + 2.
ASCII: 61 =  x3D.
==
Equal comparison. EG: 5=="5".
>
Right angle bracket. Right chevron.
Greater than symbol.
&gt; in HTML and XML.
Often used to enclose tags (descriptions of syntactic elements) in SGML, HTML, XML, and such. EG: <head>.
ASCII: 62 =  x3E.
>>
Much greater than symbol. EG: 1000 >> 1.
>=
Greater than or equal to symbol. Other symbols used include: .
?
Question mark.
Denotes a wildcard for a single character.
Denotes zero or one.
Denotes a querystring in URLs. EG: www.fake.com?x=23&y=71.
ASCII: 63 = x3F.
@
At. A symbol for the word "at". EG: I am sitting @ my computer. The symbol is commonly used as part of e-mail addresses in the following format: user@host.com.

In the Middle Ages, monks used the @ symbol as an abbreviation for "ad", which is Latin for "at" since they wrote their d's in a curly way. In the 15th century Spanish merchants used the @ symbol as an abbreviation for "arroba", which is a unit of mass (about 25.40 lb or 11.52 kg) used for for things like wine and bulls. Since the Renaissance people have used the @ symbol to mean "at the following price". EG: "beer@$3" means "beer at $3 each".

The Germans call the @ symbol klammeraffe ("spider monkey"), the French petit escargot ("little snail"). I hear that the Swedes call it elephant's ear or cinnamon bun, and the Finlanders call it a cat's tail.

ASCII: 64 =  x40.
A-Z
These are alphabetic uppercase letters.
ASCII: 65-90 =  x41-x5A.
[
Left bracket.
Often used to enclose optional elements.
ASCII: 91 = x5B.
\
Back slash.
Used to separate directories in DOS and Windows.
Often used to denote integer division, i.e. division where the remainder (modulus) is discarded. EG: 9\4 is 2.
Indicates an escaped character, i.e. a character that would mean something else in context. The most famous escapes include:
  • In C family programming languages:
    • \b = BS = backspace. ASCII: 8 = x8 = ^H.
    • \t = HT = tab. ASCII: 9 = x9 = ^I.
    • \n = LF (Line Feed) = NL (New Line) = EOL (End Of Line). Unix EOL (Win EOL is \r\n). ASCII: 10 = xA = ^J.
    • \v = VT = vertical tab. ASCII: 11 = xB = ^K.
    • \f = NP (New Page, page eject) = FF (Form Feed). ASCII: 12 = xC = ^L.
    • \r = CR (Carriage Return). Mac EOL (Win EOL is \r\n). ASCII: 13 = xD = ^M.
    • \e = ESC (ESCape), next character not echoed. ASCII: 27 = x1B = ^[.
    • \" = double quote. ASCII: 34 =  x22.
    • \' = single quote. ASCII: 39 =  x27.
  • In regular expressions:
    • \f, \n, \r, \t, \v as above.
    • \b = word boundary. EG: "er\b" matches "er" in "hover x" but not the "er" in "Ebert".
    • \B = non-word boundary. EG: "er\B" matches "er" in "Ebert" but not the "er" in "hover x".
    • \cx = Matches a control character x, where x is A-Z or a-z.
    • \d = Matches a digital character. Same as [0-9].
    • \D = Matches a non-digital character. Same as [^0-9].
    • \s = Matches a whitespace character. Same as "[\f\n\r\t\v]".
    • \S = Matches a non-whitespace character. Same as "[^\f\n\r\t\v]".
    • \w = Matches a word character. Same as "[A-Za-z0-9_]".
    • \W = Matches a non-word character. Same as "[^A-Za-z0-9_]".
    • \on = Matches an ASCII octal character code n. JavaScript only. EG: "\x5a" matches "Z".
    • \xn = Matches an ASCII hexadecimal character code n. In VBScript, n must be 2 digits. EG: "\x5a" matches "Z".
    • \un = Matches a Unicode hexadecimal character code n, where n has 4 digits. EG: "\u00A2" matches "?".

ASCII: 92 =  x5C.
 ]
Right bracket.
Often used to enclose optional elements.
ASCII: 93 = x5D.
^
Caret.
Control.
Often used to note exponentiation (raising to an power). EG: 10^2 is ten squared or 100.
In regular expressions, this matches at the beginning of the target string.
In regular expressions, this means not the set. EG: "[^x-z]" matches any character except for "x, "y", or "z".
ASCII: 94 =  x5E.
_
Underscore.
ASCII: 95 =  x5F.
`
Back quote. Grave symbol.
ASCII: 96 = x60.
a-z
These are alphabetic lowercase letters.
ASCII: 97-122 = x61-x7A.
{
Left curly brace.
Often used to enclose two or more options. EG: x = {a | b | c} is like x is a, b, or c.
ASCII: 127 = x7B.
|
Vertical bar. Pipe.
Denotes an additional argument for a command or function.
Separate two or more arguments, of which only one can be chosen. x = {a | b | c} is like x is a, b, or c.
In Unix and Linux, the pipe transfers the output to another application.
ASCII: 128 = x7C.
II
Logical OR. EG: true || false.
}
Right curly brace.
Often used to enclose two or more options. EG: x = {a |b | c} is like x is a, b, or c.
ASCII: 129 = x7D.
~
Tilde.
Swung dash.
Approximate symbol. Other symbols used include: .
Denotes a users home directory. EG: ~john or http:/fake.com/~john may mean /home/john.
&tilde;
ASCII: 130 = x7E.

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