address such as firstname.lastname@example.org that does not have a corresponding
POP3 mailbox set up.
For example, if you have a default POP3 mailbox called sales (i.e.
email@example.com), and you have not created any other mailboxes,
e-mail addressed to firstname.lastname@example.org will be sent to the sales
mailbox. If someone were to e-mail email@example.com, in this
example, that mail would also be forwarded to the sales mailbox.
of program that searches your hard drive, floppy disks, and e-mail
for any known or potential viruses.
The market for this kind of program has expanded because of Internet
growth, the widespread publicity surrounding some recent computer
viruses, and the increasing use of the Internet by businesses concerned
about protecting their computer assets.
Registry of Internet Numbers) - The organization that manages IP
address numbers for the U.S. and assigned territories. Because
addresses must be unique and because the number of addresses available
is limited, there is a need for some organization to control and allocate
address number blocks.
Standard Code for Information Interchange) - The most common format
for text files in computers and on the Internet.
In an ASCII file, each alphabetic, numeric, or special character is
represented with a 7-bit
binary number (a string of seven 0s or 1s). 128 (27) possible
characters are defined.
|| A program
or script used to send automated responses to incoming e-mail
messages sent to a specific e-mail address. For example, an auto responder
could be used to send a standard message acknowledging receipt of
the incoming message and indicating when the message will be acted
|| A high-speed
communication link or series of links that forms a major trunk within
a network. The
term is relative, as a backbone in a small network may be much smaller
than many non-backbone links in a large network.
|| The throughput
capacity of a network measured in bps.
|| A unit
of data transfer equal to the number of binary values (bits)
transmitted per second. Baud is equivalent to bps.
In communications usage, the baud rate of a modem is how many bits
it can send or receive per second.
|| A binary
(base-2) number, either a 0 (zero) or a 1 (one); the smallest unit
of digital data.
"robot") - A program that operates as an agent for a user
or another program or simulates a human activity. On the Internet,
the most common bots are the programs that access web
sites and gather their content for search
engines. Bots are also called 'spiders' or 'crawlers'.
- The rate of data movement between two places. A 28.8K modem can
move 28,800 bits-per-second.
|| A group
of bits that represent
a single alphanumeric character. There are 8 data bits in a byte,
but there may be additional bits associated with each byte for other
purposes such as error detection and correction.
Gateway Interface) - A set of rules that describe how a web
server software application communicates with another piece of
software on the same computer (server),
and how the other piece of software (the 'CGI program') talks to the
web server. Any piece of software can be a CGI program if it handles
input and output according to the CGI standard. Usually a CGI program
is a small program that takes data from a web server and does something
with it, like putting the content of a form into an e-mail
message, or converting the data into a database
|| The most
common name of the directory on a web
server in which CGI
programs are stored. The 'bin' part of cgi-bin is a shortened version
of 'binary', because once upon a time, most programs were referred
to as 'binaries'. In real life, most programs found in cgi-bin directories
are text files - scripts
that are executed by programs located elsewhere on the server.
While most CGI scripts are stored in this directory, it is not a requirement
for using CGI.
|| A software
program that is used to contact and obtain data from a server
software program on the same computer or on another computer, often
across a great distance. Each client program is designed to work with
one or more specific kinds of server programs, and each server requires
a specific kind of client. A web
browser and an e-mail
reader are examples of clients.
the relationship between two computer programs in which one program
(the client) makes
a request from another program (the server)
that fulfills the request. Although programs within a single computer
can use the client/server relationship, it is a more important idea
in a network.
In a network, the client/server model provides a convenient way to
interconnect programs that are distributed efficiently across different
locations. Computer transactions using the client/server model are
very common. Other program relationship models include master/slave,
with one program being in charge of all other programs, and peer-to-peer,
with either of two programs able to initiate a transaction.
|| The most
common meaning of 'cookie' on the Internet refers to a piece of information
sent by a web server
to a web browser
that the browser software is expected to save and to send back to
the server whenever
the browser makes additional requests from the server. Depending on
the type of cookie used, and the browser's settings, the browser may
or may not accept the cookie, and may save the cookie for either a
short time or a long time. Cookies might contain information such
as login or registration
information, online 'shopping
cart' information, or user preferences. When a server receives
a request from a browser that includes a cookie, the server is able
to use the information stored in the cookie. For example, the server
might customize what is sent back to the user, or keep a log of a
particular user's requests.
||A list of
one or more commands to a computer operating system or application
server that are
to be executed at a specified time. Each command is executed when
its triggering time arrives. In UNIX-based
systems, the 'crontab' command is a user interface command that
creates or changes a file (called a crontab file). This file contains
a list of UNIX shell
commands, each with a specified time of execution. A CRON script is
DEE-muhn) - A program that runs continuously and exists for the purpose
of handling periodic service requests that a computer system expects
to receive. The daemon program forwards the requests to other programs
(or processes) as appropriate. Each web
server on the Internet
has an HTTPD (or HyperText Transfer Protocol daemon) that continually
waits for requests to come in from web clients and their users.
A database is a collection of data that is organized so that its
contents can easily be accessed, managed, and updated. The most
prevalent type of database is the relational database, a tabular
database in which data is defined so that it can be reorganized
and accessed in a number of different ways. A distributed database
is one that can be dispersed or replicated among different points
in a network. An object-oriented programming database is one that
is congruent with the data defined in object classes and subclasses.
Databases contain aggregations of data records or files, such as
sales transactions, product catalogs and inventories, and customer
profiles. Typically, a database manager provides users the capabilities
of controlling read/write access, specifying report generation,
and analyzing usage. Databases and database managers are prevalent
in large mainframe systems, in smaller distributed workstation and
midrange systems, and on personal computers. SQL
is a standard language for making interactive queries and updating
records in relational databases, including those from IBM, Microsoft,
Oracle, Sybase, Informix, and Computer Associates.
data from a web
to a client. For
example - each time an HTML
file, an image, or other element on a web
page is sent from the server to a client, data transfer is generated.
Web site hosting packages frequently define the maximum allowable
free data transfer per month. Additional data transfer can result
in additional web hosting charges.
of converting encrypted
data back into its original form, so it can be understood.
use of a computer, related server
software, and connection to the Internet,
that is owned by and housed in the web
hosting company's location. A dedicated server is usually needed
for a large web site
(or set of related company sites) that may develop a large amount
of traffic. The use of a dedicated server at the web hosting company
saves router, Internet
connection, security system, and network administration costs for
the site's owner.
daily graphical reports on a web
site's visitor demographics generated from raw
log files by a program such as 'The Webalizer' or 'AwStats'. These
statistics allow the owner or manager to monitor how much traffic
the web site receives.
"ID card" that establishes the credentials of someone doing
business or other transactions on the Web. It is issued by a certification
authority (CA). It contains the owner's name, a serial number, expiration
date, a copy of the certificate holder's public key (used for encrypting
messages and digital signatures), and the digital signature of the
certificate-issuing authority so that a recipient can verify that
the certificate is real.
|| The amount
of server disk
storage a web site
is allocated. This space is used to store HTML
files, graphics, e-mail
messages, and all other files that make up a web site. One megabyte
(MB) of disk space can hold several hundred pages of text and images.
Web site hosting packages usually define the maximum disk space a
web site can consume. Additional disk space used can result in additional
web hosting charges.
Name System) - The way that Internet
are located and translated into IP
addresses. A domain name is a meaningful and easy-to-remember
'handle' for an IP address. Because maintaining one central list of
domain name-to-IP address correspondences would be impractical (because
of the tremendous network
traffic), the lists of domain names and IP addresses are distributed
throughout the Internet in a hierarchy of authority. Each ISP
uses a DNS server
(also called a name
server) that is usually geographically
local to map the domain names in Internet requests to IP addresses
or else forward them to another, higher level DNS server to process.
|| The unique
name that identifies an Internet
and maps it to a specific IP
address. Domain names always have 2 or more parts, separated by
periods (dots). For example, the domain name www.ShenValleyOnline.net
maps the domain 'shenvalleyonline.net' to IP address 184.108.40.206,
which is the IP addres of the server where this web site is located.
This domain name has three parts: The 'net' part of the domain name
is the most general part and is called the top-level
domain name. It reflects the purpose of the web site ('net' refers
to 'network', 'com' refers to 'commercial, etc.). The 'ShenValleyOnline'
part identifies the organization and, with the top-level, is called
domain name. The 'www'
part denotes the name of a server
that provides responses to Internet requests. It is also possible
for a domain name to exist but not have a web site on a server. This
is often done so that an organization or business can have an Internet
e-mail address without
having to establish a real Internet site. In these cases, there must
be a server to handle e-mail on behalf of the domain name.
of registering a unique second-level
domain name with one of the ICANN-accredited
registrars for the .biz, .com, .net, .org, and other
System) - MS-DOS was the first widely-installed operating
system for personal computers. It has a relatively simple line-oriented,
command-driven, but not overly 'friendly' user interface.
Digital Signal X) -The series of standard digital transmission
rates or levels based on a transmission rate of 64 Kbps (DS0), the
bandwidth normally used for one telephone voice channel. Both the
North American T-carrier system system and the European E-carrier
systems use the DS series as a base multiple. The digital signal
is what is carried inside the carrier system.
DS0 is the base for the digital signal X series. DS1, used as the
signal in the T-1
carrier, is 24 - multiplexed DS0 signals. DS2 is four DS1 signals
multiplexed together to produce a rate of 6.312 Mbps. DS3, the signal
in the T-3 carrier, carries a multiple of 28 DS1 signals or 672
DS0 signals or 44.736 Mbps.