|
Click on the links below
to find information on any part of Internet lingo.
Apache
A public-domain
Web server developed by a loosely-knit group of programmers. The first
version of Apache, based on the NCSA httpd Web server, was developed in
1995. Because it was developed from existing NCSA code plus various patches,
it was called a patchy server - hence the name Apache Server.
As a result
of its sophisticated features, excellent performance, and low price (it's
free), Apache has became the world's most popular Web server. By some estimates,
it is used to host more than 50% of all Web sites in the world. Core
development of the Apache Web server is performed by a group of about 20
volunteer programmers, called the Apache Group. However, because the source
code is freely available, anyone can adapt the server for specific needs,
and there is a large public library of Apache add-ons. In many respects,
development of Apache is similar to development of the Linux operating
system. The original version of Apache was written for UNIX, but there
are now versions that run under other platforms.
ASCII
Used in FTP
and the WWW, this is a type of file, usually any kind of file that you
can read (like a text file) falls under this classification (HTML files
should be ASCII files).
ASP
A specification
for a dynamically created Web page with a .ASP extension that contain either
Visual Basic or Jscript code. When a browser requests an ASP page, the
Web server generates a page with HTML code and sends it back to the browser.
So ASP pages are similar to CGI scripts, but they enable Visual Basic programmers
to work with familiar tools.
Bandwidth
The amount
of data that can be transmitted in a fixed amount of time. For digital
devices, the bandwidth is usually expressed in bits per second(bps) or
bytes per second. For analog devices, the bandwidth is expressed in cycles
per second, or Hertz (Hz).
The bandwidth
is particularly important for I/O devices. For example, a fast disk drive
can be hampered by a bus with a low bandwidth. This is the main reason
that new buses, such as AGP, have been developed for the PC.
Binary
Used in FTP
and the WWW, this is a type of file, usually any kind of file that is unreadable
as text falls under this classification (graphic images, sound files, etc.
should be BINARY files)
Blue
Screen of Death
An error that
can appear on computers running Microsoft Windows XP or Vista. Jokingly
called the blue screen of death because when the error occurs, the screen
turns blue, and the computer almost always freezes and requires rebooting.
Browser
Short for Web
browser, a software application used to locate and display Web pages. The
two most popular browsers are Microsoft Internet
Explorer, FireFox, and Safari.
C++
An object oriented
language that can be compiled and run on a server via the source file of
sample.c and then compiled into an executable file.
Cache
Pronounced
cash, a special high-speed storage mechanism. It can be either a reserved
section of main memory or an independent high-speed storage device. Two
types of caching are commonly used in personal computers: memory caching
and disk caching.
A memory cache,
sometimes called a cache store or RAM cache, is a portion of memory made
of high-speed static RAM (SRAM) instead of the slower and cheaper dynamic
RAM (DRAM) used for main memory. Memory caching is effective because most
programs access the same data or instructions over and over. By keeping
as much of this information as possible in SRAM, the computer avoids accessing
the slower DRAM.
Some memory
caches are built into the architecture of microprocessors. The Intel 80486
microprocessor, for example, contains an 8K memory cache, and the Pentium
has a 16K cache. Such internal caches are often called Level 1 (L1) caches.
Most modern PCs also come with external cache memory, called Level 2 (L2)
caches. These caches sit between the CPU and the DRAM. Like L1 caches,
L2 caches are composed of SRAM but they are much larger.
Disk caching
works under the same principle as memory caching, but instead of using
high-speed SRAM, a disk cache uses conventional main memory.
The most recently
accessed data from the disk (as well as adjacent sectors) is stored in
a memory buffer. When a program needs to access data from the disk, it
first checks the disk cache to see if the data is there. Disk caching can
dramatically improve the performance of applications, because accessing
a byte of data in RAM can be thousands of times faster than accessing a
byte on a hard disk.
When data is
found in the cache, it is called a cache hit, and the effectiveness of
a cache is judged by its hit rate. Many cache systems use a technique known
as smart caching, in which the system can recognize certain types of frequently
used data. The strategies for determining which information should be kept
in the cache constitute some of the more interesting problems in computer
science.
CGI
Abbreviation
of Common Gateway Interface, a specification for transferring information
between a World Wide Web server and a CGI program. A CGI program is any
program designed to accept and return data that conforms to the CGI specification.
The program could be written in any programming language, including C,
Perl, Java, or Visual Basic. CGI programs are the most common way
for Web servers to interact dynamically with users. Many HTML pages that
contain forms, for example, use a CGI program to process the form's data
once it's submitted. Another increasingly common way to provide dynamic
feedback for Web users is to include scripts or programs that run on the
user's machine rather than the Web server. These programs can be Java applets,
Java scripts, or ActiveX controls. These technologies are known collectively
as client-side solutions, while the use of CGI is a server-side solution
because the processing occurs on the Web server.
One problem
with CGI is that each time a CGI script is executed, a new process is started.
For busy Web sites, this can slow down the server noticeably. A more efficient
solution, but one that it is also more difficult to implement, is to use
the server's API, such as ISAPI or NSAPI. Another increasingly popular
solution is to use Java servlets.
Cron
A Unix command
for scheduling jobs to be executed sometime in the future. A cron is normally
used to schedule a job that is executed periodically - for example, to
send out a notice every morning. It is also a daemon process, meaning that
it runs continuously, waiting for specific events to occur.
DNS
(1) Short for
Domain Name System (or Service), an Internet service that translates domain
names into IP addresses. Because domain names are alphabetic, they're easier
to remember. The Internet however, is really based on IP addresses. Every
time you use a domain name, therefore, a DNS service must translate the
name into the corresponding IP address. For example, the domain name www.example.com
might translate to 198.105.232.4. The DNS system is, in fact, its
own network. If one DNS server doesn't know how to translate a particular
domain name, it asks another one, and so on, until the correct IP address
is returned.
DHTML
Dynamic HTML
(1) refers
to Web content that changes each time it is viewed. For example, the same
URL could result in a different page depending on any number of parameters,
such as:
-
Geographic location
of the reader
-
Time of day
-
Previous pages
viewed by the reader
-
Profile of the
reader
There are many
technologies for producing dynamic HTML, including CGI scripts, Server-Side
Includes (SSI), cookies, Java, JavaScript, and ActiveX.
(2) When capitalized,
Dynamic HTML refers to new HTML extensions that will enable a Web page
to react to user input without sending requests to the Web server. Microsoft
and Netscape have submitted competing Dynamic HTML proposals to W3C, which
is producing the final specification.
Email
Alias
Aliasing allows
you to have multiple e-mail addresses sent to a specific POP e-mail account
(ie. pick up webmaster@your-actual-domain.com, sales@your-actual-domain.com, etc. from
one POP account rather than from several separate ones).
Email
Forward
Forwarding
allows you to have e-mail forwarded from a specific address or POP account
to another POP account (ie. have all e-mail sent to webmaster@your-actual-domain.com
sent to your POP account provided by your ISP).
Firewall
A system designed
to prevent unauthorized access to or from a private network. Firewalls
can be implemented in both hardware and software, or a combination of both.
Firewalls are frequently used to prevent unauthorized Internet users from
accessing private networks connected to the Internet, especially intranets.
All messages entering or leaving the intranet pass through the firewall,
which examines each message and blocks those that do not meet the specified
security criteria.
There are several
types of firewall techniques:
Packet filter:
Looks at each packet entering or leaving the network and accepts or rejects
it based on user-defined rules. Packet filtering is fairly effective and
transparent to users, but it is difficult to configure. In addition, it
is susceptible to IP spoofing.
Application
gateway: Applies security mechanisms to specific applications, such
as FTP and Telnet servers.
This is very
effective, but can impose a performance degradation.
Circuit-level
gateway: Applies security mechanisms when a TCP or UDP connection is
established. Once the connection has been made, packets can flow between
the hosts without further checking. Proxy server: Intercepts all
messages entering and leaving the network. The proxy server effectively
hides the true network addresses. In practice, many firewalls use
two or more of these techniques in concert. A firewall is considered
a first line of defense in protecting private information. For greater
security, data can be encrypted.
FTP
Abbreviation
of File Transfer Protocol, the protocol used on the Internet for sending
files.
HTML
Short for HyperText
Markup Language, the authoring language used to create documents on the
World Wide Web. HTML is similar to SGML, although it is not a strict subset.
InterNIC
The regulatory
agency that handles the assignment and database tracking of active/inactive/available
domain names. Each country has their own NIC registry service for handling
foreign (or domestic) domain names.
IPP
(Internet Presence
Provider) provides presences on the Internet, usually provides web hosting
and e-mail services (this is what we do).
ISP
(Internet Service
Provider) provides connectivity to the Internet, usually via modem and
dialup lines (we DO NOT provide ISP services)
Java
Java: A high-level
programming language developed by Sun Microsystems. Java was originally
called OAK, and was designed for handheld devices and set-top boxes. Oak
was unsuccessful so in 1995 Sun changed the name to Java and modified the
language to take advantage of the burgeoning World Wide Web. Java is an
object-oriented language similar to C++, but simplified to eliminate language
features that cause common programming errors. Java source code files (files
with a .java extension) are compiled into a format called bytecode (files
with a .class extension), which can then be executed by a Java interpreter.
Compiled Java code can run on most computers because Java interpreters
and runtime environments, known as Java Virtual Machines (VMs), exist for
most operating systems, including UNIX, the Macintosh OS, and Windows.
Bytecode can also be converted directly into machine language instructions
by a just-in-time compiler (JIT). Java is a general purpose programming
language with a number of features that make the language well suited for
use on the World Wide Web. Small Java applications are called Java applets
and can be downloaded from a Web server and run on your computer by a Java-compatible
Web browser, such as Netscape Navigator or Microsoft Internet Explorer.
Kernel
The kernel
is the core of the operating system. It's primary functions are controlling
execution of processes, handling memory management, providing a file system,
and providing a portable interface through which programs may communicate
with hardware.
Linux
A freely-distributable implementation of UNIX that runs on a
number of hardware platforms, including Intel and Motorola microprocessors.
It was developed mainly by Linus Torvalds. Because it's free, and because
it runs on many platforms, including PCs, Macintoshes and Amigas, Linux
has become extremely popular over the last couple years. Another popular,
free version of UNIX that runs on Intel microprocessors is FreeBSD.
Perl
Short for Practical
Extraction and Report Language, Perl is a programming language developed
by Larry Wall, especially designed for processing text. Because of its
strong text processing abilities, Perl has become one of the most popular
languages for writing CGI scripts. Perl is an interpretive language, which
makes it easy to build and test simple programs.
POP
(Point of Presence)Physical
e-mail accounts you log into with a username and password to pick up any
e-mail sent/forwarded to that account
Propogation
A period after
a domain name is registered or transferred when the domain name is updated
amoung all the nameservers found on the Internet around the world. This
period usually lasts 3-7 days and may result in visitors not being able
to visit the domain name until the period is over.
Router
Router: A device
that connects two LANs. Routers are similar to bridges, but provide additional
functionality, such as the ability to filter messages and forward them
to different places based on various criteria. The Internet uses routers
extensively to forward packets from one host to another.
RSA
Encryption
is based on
a public key system which means that every user has 2 digital keys one
to encrypt information, and the other to decrypt. Authentication of both
sender and recipient is provided with this method.
SCSI
SCSI (Small
Computer Systems Interface) SCSI (pronounced "scuzzy") differs in a big
way from the ST-506 standard. SCSI is actually a smart bus - it is controlled
with a microprocessor - and it allows the addition of up to seven devices
(not necessarily just hard drives - scanners, printers and other devices
often use SCSI) to the computer. SCSI drives are also usually large and
fast. Using one will require the addition of a SCSI adapter. In the early
days of SCSI, a lot of devices were made that didn't talk to each other,
but those days are behind us for the most part. SCSI II is a newer standard
which allows data transfer rates that are a lot higher than the older SCSI
standard. SCSI and SCSI II devices should be able to coexist on a SCSI
II bus. There are also Fast SCSI and Wide SCSI, two standards that allow
even greater bandwidth across the SCSI bus. These two standards are most
often seen on high end workstations or file servers. The latest SCSI standard
is SCSI III. At this point in time, a few SCSI III drives, cables and controllers
are available. Each SCSI device on the SCSI bus requires a unique SCSI
number, from 1 to 7 (the computer's SCSI number is 0). SCSI devices are
daisy chained together by cabling, and the device at the end of the daisy
chain has to have a terminator resistor.
Shell
The outermost
layer of a program. Shell is another term for user interface. Operating
systems and applications sometimes provide an alternative shell to make
interaction with the program easier. For example, if the application is
usually command driven, the shell might be a menu-driven system that translates
the user's selections into the appropriate commands. (2) Sometimes called
command shell, a shell is the command processor interface. The command
processor is the program that executes operating system commands. The shell,
therefore, is the part of the command processor that accepts commands.
After verifying that the commands are valid, the shell sends them to another
part of the command processor to be executed. UNIX systems offer a choice
between several different shells, the most popular being the Cshell, the
Bourne shell, and the Korn shell. Each offers a somewhat different command
language.
Shopping
Cart
is a piece
of software that operates on an online storefront. The "shopping cart"
keeps track of all the items that a buyer wants to purchase, allowing the
shopper to pay for the whole order at once.
SMTP
Short for Simple
Mail Transfer Protocol, a protocol for sending e-mail messages between
servers. Most e-mail systems that send mail over the Internet use SMTP
to send messages from one server to another; the messages can then be retrieved
with an e-mail client using either POP or IMAP. In addition, SMTP is generally
used to send messages from a mail client to a mail server. This is why
you need to specify both the POP or IMAP server and the SMTP server when
you configure your e-mail application.
SONET
SONET stands
for Synchronous Optical NETwork. The SONET format allows different types
of formats to be transmitted on one line. SONET is a long term solution
for a mid-span-meet between vendors. The other major advantage is that
SONET allows ADDING and DROPING signals with a single multiplexer.
SSI
Short for server-side
include, a type of HTML comment that directs the Web server to dynamically
generate data for the Web page whenever it is requested. The basic format
for SSIs are <!--#command tag="value"> Where #command can be any of
various commands supported by the Web server. The simplest command is #include,
which inserts the contents of another file. This is especially useful for
ensuring that boilerplate components, such as headers and footers, are
the same on all pages throughout a Web site. To change a boilerplate element,
you need only modify the include file, instead of updating every individual
Web page. SSIs can also be used to execute programs and insert the results.
They therefore represent a powerful tool for Web developers. There is no
official standard for SSIs, so every Web server is free to support different
SSIs in different manners. However, many SSI commands, such as #include
and #exec, have become de facto standards. Web pages that contain SSIs
often end with a .shtml extension, though this is not a requirement. The
filename extension enables the Web server to differentiate those pages
that need to be processed before they are sent to the browser.
Telnet
A terminal
emulation program for TCP/IP networks such as the Internet. The Telnet
program runs on your computer and connects your PC to a server on the network.
You can then enter commands through the Telnet program and they will be
executed as if you were entering them directly on the server console. This
enables you to control the server and communicate with other servers on
the network. To start a Telnet session, you must log in to a server by
entering a valid username and password. Telnet is a common way to remotely
control Web servers.
UNIX
Pronounced
yoo-niks, a popular multi-user, multitasking operating system developed
at Bell Labs in the early 1970s. Created by just a handful of programmers,
UNIX was designed to be a small, flexible system used exclusively by programmers.
Although it has matured considerably over the years, UNIX still betrays
its origins by its cryptic command names and its general lack of user-friendliness.
This is changing, however, with graphical user interfaces such as MOTIF.
UNIX was one of the first operating systems to be written in a high-level
programming language, namely C. This meant that it could installed on virtually
any computer for which a C compiler existed. Due to its portability, flexibility,
and power, UNIX has become the leading operating system for workstations.
Historically, it has been less popular in the personal computer market,
but the emergence of a new version called Linux is revitalizing UNIX across
all platforms
URL
Abbreviation
of Uniform Resource Locator, the global address of documents and other
resources on the World Wide Web. The first part of the address indicates
what protocol to use, and the second part specifies the IP address or the
domain name where the resource is located. For example, the two URLs below
point to two different files at the domain pcwebopedia.com. The first specifies
an executable file that should be fetched using the FTP protocol; the second
specifies a Web page that should be fetched using the HTTP protocol:
WWW
(World Wide
Web) refers to the vast web sites and such that span the Internet. |
