Most personal computers today are sold as
stand-alone, self-sufficient units that are
equipped with all the necessary hardware
and software needed to operate independently.
In other words, they can perform
input, processing, output, and storage without
being connected to a network, although
they can be networked if desired. In contrast,
a device that must be connected to a
network to perform processing or storage
tasks is referred to as a dumb terminal. Two
types of personal computers that may be able to perform a limited amount of independent
processing but are designed to be used with a network are thin clients and Internet
A thin client is designed to utilize a company network for much of its processing
capabilities. Instead of using local hard drives for storage, programs are typically accessed
from and data is stored on a network server. The main advantage of thin clients over desktop
computers is lower cost because hardware needs to be replaced less frequently, and
costs are lower for computer maintenance, power, and air conditioning. Additional benefits
include increased security (because data is not stored on the computer) and easier maintenance
(because all software is located on a central server). Disadvantages include having
limited or no local storage (although this is an advantage for companies with highly secure
data that need to prevent data from leaving the facility) and not being able to function as
a stand-alone computer when the network is not working. Thin clients are used by businesses
to provide employees with access to network applications; they are also used in
school computer labs.
|How Thin Client Works|
Gaming consoles (such as the Nintendo Wii, the Xbox 360 and the Sony PlayStation 3) that can be used to view Internet content, in
addition to their gaming abilities, can also be classified as Internet appliances when they
are used to access the Internet.
Virtually any device (such as
a smartphone) being used to
access a company network
or cloud resource can also be
referred to as a “thin client” while
it is being used for that purpose.
Ordinary devices that can be used for accessing the Internet can be called
Internet appliances (sometimes referred to as Internet-enabled devices). Some Internet
appliances (such as smart TVs and the smart refrigerator use
apps to deliver news, sports scores, weather, music, and other Web-based information.
>Thin client. A personal computer designed to access a network for processing and data storage, instead of performing those tasks locally.
>Internet appliance. A device that can be used to access the Internet.
A server—also sometimes called a mid-range server, minicomputer, or mid-range computer—
is a computer used to host programs and data for a small network. Typically larger,
more powerful, and more expensive than a desktop computer, a server is usually located in
an out-of-the-way place and can serve many users at one time. Users connect to the server
through a network, using their desktop computer, portable computer, thin client, or a dumb
terminal consisting of just a monitor and keyboard. Servers are often
used in small- to medium-sized businesses (such as medical or dental offices), as well as in
school computer labs. There are also special home servers designed for home use, which
are often used to back up (make duplicate copies of) the content located on all the computers
in the home automatically and to host music, photos, movies, and other media to be
shared via a home network.
One trend involving servers (as well as the mainframe computers discussed next)
today is Virtualization—creating virtual (rather than actual) versions of a computing
resource. Server Virtualization uses separate server environments that, although physically
located on the same computer, function as separate servers and do not interact with
each other. For instance, all applications for an organization
can be installed in virtual environments on one or more physical
servers instead of using a separate server for each application.
Using a separate server for each application often wastes
resources because the servers are typically not used to full
capacity—one estimate is that only about 10% of server capability
is frequently utilized. With Virtualization, companies
can fulfill their computing needs with fewer servers, which
results in lower costs for hardware and server management, as
well as lower power and cooling costs. Consequently, one of
the most significant appeals of Server Virtualization today is
Server. A computer used to host programs and data for a small network. >Virtualization. Creating virtual (rather than actual) versions of a
computing resource, such as several separate environments that are located on a single server but function as different servers.
With the wide use of portable computers and mobile
devices in the workplace, desktop virtualization is a growing
trend. Desktop virtualization separates the user’s desktop environment
from his or her physical computer so that each user’s
desktop (stored on a central server) can be delivered to that
individual via any authorized device; the user interacts with the
virtual desktop in the same way he or she would interact with a physical desktop. Desktop virtualization adds flexibility to where and how each worker
performs daily tasks. Virtualization is also used in other computing areas, such as networking
A mainframe computer is a powerful computer used by many large organizations—
such as hospitals, universities, large businesses, banks, and government offices—that
need to manage large amounts of centralized data. Larger, more expensive, and more
powerful than servers, mainframes can serve thousands of users connected to the mainframe
via personal computers, thin clients, or dumb terminals, in a manner similar to
the way users connect to servers. Mainframe computers are typically located in climate-controlled
data centers and are connected to the rest of the company
computers via a computer network. During regular business hours, a mainframe typically
runs the programs needed to meet the different needs of its wide variety of users.
At night, it commonly performs large processing tasks, such as payroll and billing.
Today’s mainframes are sometimes referred to as high-end servers or enterprise-class
servers and they usually cost at least several hundred thousand
Some applications require extraordinary speed, accuracy, and processing capabilities—
for example, sending astronauts into space, controlling missile guidance systems
and satellites, forecasting the weather, exploring for oil, breaking codes, and designing
and testing new products. Supercomputers—the most powerful and most expensive
type of computer available—were developed to fill this need. Some relatively new
super-computing applications include hosting extremely complex Web sites (such as
search sites and social networking sites) and three-dimensional applications (such as
3D medical imaging, 3D image projections, and 3D architectural modeling). Unlike
mainframe computers, which typically run multiple applications simultaneously to
serve a wide variety of users, supercomputers generally run one program at a time, as
fast as possible.
Conventional supercomputers can cost several million dollars each. They tend to be
very large and contain a large number of CPUs. For example, the Titan supercomputer
occupies 4,352 square feet of floor space and contains 299,008 CPUs. This supercomputer is being installed at the U.S. Department of Energy Oak Ridge National Laboratory and is expected to be used for a variety of scientific research, including climate change and astrophysics; its speed is expected to give researchers unparalleled accuracy in their simulations and facilitate faster research breakthroughs. At 17.59 petaflops (quadrillions of floating point operations or calculations per second) at the present time and expected to surpass 20 petaflops when completed, Titan is one of the
fastest computers in the world.
.As best I understand, a petaflop is 1,000 trillion connections per second. The human brain can do 20,000 of them, so it's the high mark for computer
>Mainframe computer. A computer used in large organizations (such as hospitals, large businesses, and colleges) that need to manage large
amounts of centralized data and run multiple programs simultaneously. >Supercomputer. The fastest, most expensive, and most powerful type of computer.
COMPUTER NETWORKS AND THE INTERNET
A computer network is a collection of computers and other devices that are connected
together to enable users to share hardware, software, and data, as well as to
communicate electronically with each other. Computer networks exist in many sizes
and types. For instance, home networks are commonly used to allow home computers
to share a single printer and Internet connection, as well as to exchange files.
Small office networks enable workers to access company records stored on a network
server, communicate with other employees, share a high-speed printer, and access the
Internet. School networks allow students and teachers to access
the Internet and school resources, and large corporate networks often connect all of the
offices or retail stores in the corporation, creating a network that spans several cities or
states. Public wireless networks—such as those available at some coffeehouses, restaurants,
public libraries, and parks—provide Internet access to individuals via their
portable computers and mobile devices; mobile telephone networks provide Internet
access and communications capabilities to smartphone users. Most computers today
connect to a computer network.
What Are the Internet and the World Wide Web?
>Computer network. A collection of computers and other hardware devices that are connected together to share hardware, software, and data, as
well as to communicate electronically with one another. >Internet. The largest and most well-known computer network, linking millions of computers
all over the world. >Internet service provider (ISP). A business or other organization that provides Internet access to others, typically for a fee.
The Internet is the largest and most well-known computer network in the world. It is technically
a network of networks because it consists of thousands of networks that can all
access each other via the main backbone infrastructure of the Internet. Individual users
connect to the Internet by connecting their computers or other devices to servers belonging
to an Internet service provider (ISP)—a company that provides Internet access, usually
for a fee. ISPs (which include conventional and mobile telephone companies like AT&T,
Verizon, and Sprint; cable providers like Comcast and Time Warner; and stand-alone ISPs
like NetZero and EarthLink) function as gateways or on ramps to the Internet, providing
Internet access to their subscribers. ISP servers are continually connected to a larger network,
called a regional network, which, in turn, is connected to one of the major high-speed
networks within a country, called a backbone network. Backbone networks within a
country are connected to each other and to backbone networks in other countries. Together
they form one enormous network of networks.
Millions of people and organizations all over the world are connected to the Internet.
The most common Internet activities today are exchanging e-mail messages and accessing content located on Web pages. While the term Internet refers to the physical
structure of that network, the World Wide Web (WWW) refers to one resource—a
collection of documents called Web pages—available through the Internet. A group of
Web pages belonging to one individual or company is called a Web site. Web pages are
stored on computers (called Web servers) that are continually connected to the Internet;
they can be accessed at any time by anyone with a computer (or other Web-enabled
device) and an Internet connection. A wide variety of information is available via Web
pages, such as company and product information, government forms and publications,
maps, telephone directories, news, weather, sports results, airline schedules, and much,
much more. You can also use Web pages to shop, bank, trade stock, and perform other
types of online financial transactions; access social media like Facebook and Google+
social networking sites and blogs; and listen to music, play games, watch television
shows, and perform other entertainment-oriented activities . Web pages are viewed using a Web browser, such as Internet Explorer (IE), Chrome, Safari, Opera, or Firefox.
>World Wide Web (WWW). The collection of Web pages available through the Internet. >Web page. A document, typically containing
hyperlinks to other documents, located on a Web server and available through the World Wide Web. >Web site. A collection of related Web
pages usually belonging to an organization or individual. >Web server. A computer that is continually connected to the Internet and hosts Web
pages that are accessible through the Internet. >Web browser. A program used to view Web pages.
Accessing a Network or the Internet
To access a local computer network (such as a home network, a school or company network,
or a public wireless hotspot), you need to use a network adapter (either built into
your computer or attached to it) to connect your computer to the network. With some
computer networks you need to supply logon information (such as a username and a password)
to log on to a network. Once you are connected to the network, you can access
network resources, including the network’s Internet connection. If you are connecting to
the Internet without going through a computer network, your computer needs to use a
modem to connect to the communications media (such as a telephone line, cable connection,
or wireless signal) used by your ISP to deliver Internet content.
|ACCESSING SOCIAL NETWORKS|
You can also communicate
directly with your friends via social
networking sites, such as Facebook
and Twitter, and mobile phone text
Most Internet connections today are direct (or always-on) connections, which means
the computer or other device being used to access the Internet is continually connected to
the ISP’s computer. With a direct connection, you only need to open your Web browser to
begin using the Internet. With a dial-up connection, however, you must start the program
that instructs your computer to dial and connect to the ISP’s server via a telephone line,
and then open a Web browser, each time you want to access the Internet.
|WATCHING VIDEOS, TV SHOWS, AND MOVIES|
To request a Web page or other resource located on the Internet, its Internet address—
a unique numeric or text-based address—is used. The most common types of Internet
addresses are IP addresses and domain names (to identify computers), URLs (to identify
Web pages), and e-mail addresses (to identify people).
>Internet address. An address that identifies a computer, person, or Web page on the Internet, such as an IP address, domain name, or e-mail address
IP Addresses and Domain Names
IP addresses and their corresponding domain names are used to identify computers
available through the Internet. IP (short for Internet Protocol) addresses are numeric,
such as 220.127.116.11, and are commonly used by computers to refer to other computers.
A computer that hosts information available through the Internet (such as a Web server
hosting Web pages) usually has a unique text-based domain name (such as microsoft.com)
that corresponds to that computer’s IP address in order to make it easier for people to request Web pages located on that computer. IP addresses and domain names are unique; that is, there cannot be two computers on the Internet using the exact same IP address or exact same domain name.
Top-Level Domains (TLDs)
ORIGINAL TLDS INTENDED USE
.com Commercial businesses
.edu Educational institutions
.gov Government organizations
.int International treaty organizations
.mil Military organizations
.net Network providers and ISPs
.org Noncommercial organizations
NEWER TLDS INTENDED USE
.aero Aviation industry
.fr French businesses
.info Resource sites
.jobs Employment sites
.mobi Sites optimized for mobile devices
.pro Licensed professionals
.uk United Kingdom businesses
To ensure this, specific IP addresses are allocated to each network (such as a company network or an ISP) to be used with the computers on that network, and there is a worldwide registration system for domain name registration. When a domain name is registered, the IP address of the computer that will be hosting the Web site associated with that domain name is also registered; the Web site can be accessed using either its domain name or corresponding IP address. When a Web site is requested using corresponding IP address.When a Web site is requested using its domain name, the corresponding IP address is looked up using one of the Internet’s domain name system (DNS) servers
and then the appropriate Web page is displayed. While today’s IP addresses (called IPv4) have four parts separated by periods, the newer IPv6 addresses have six parts separated by colons in order to have significantly more unique addresses. The transition from IPv4 to IPv6 is necessary because of the vast number of devices connecting to the Internet today.
Domain names typically reflect the name of the individual or organization associated with that Web site and the different parts of a domain name are separated by a period. The far right part of the domain name (which begins with the right most period) is called the top-level domain (TLD) and traditionally identifies the type of organization or its location (such as .com for businesses, .edu for educational institutions, .jp for Web sites located in Japan, or .fr for Web sites located in France).
The part of the domain name that precedes the TLD is called the second-level domain
name and typically reflects the name of a company or an organization, a product, or an
individual. There were seven original TLDs used in the United States; additional TLDs
and numerous two-letter country code TLDs have since been created and more are in the works. More than 250 million domain names are registered worldwide.
Uniform Resource Locators (URLs)
Similar to the way an IP address or a domain name uniquely identifies a computer on the
Internet, a Uniform Resource Locator (URL) uniquely identifies a specific Web page
(including the protocol or standard being used to display the Web page, the Web server
hosting the Web page, the name of any folders on the Web server in which the Web
page file is stored, and the Web page’s filename, if needed).
>IP address. A numeric Internet address used to uniquely identify a computer on the Internet. >Domain name. A text-based Internet address
used to uniquely identify a computer on the Internet. >Uniform Resource Locator (URL). An Internet address (usually beginning with http://) that uniquely identifies a Web page.
The most common Web page protocols are Hypertext Transfer Protocol (http://) for
regular Web pages or Secure Hypertext Transfer Protocol (https://) for secure Web pages
that can safely be used to transmit sensitive information, such as credit card numbers. File
Transfer Protocol (ftp://) is sometimes used to upload and download files. The file extension
used in the Web page filename indicates the type of Web page that will be displayed
(such as .html and .htm for standard Web pages created using HTML or XHTML).
Be sure that any Web page used to
send sensitive data (such as your
Social Security number or credit
card information) is secure. Look for
a URL that starts with https instead
of http and a locked padlock icon on
the Address bar.
To contact people using the Internet, you often use their e-mail addresses. An e-mail
address consists of a username (an identifying name), followed by the @ symbol, followed
by the domain name for the computer that will be handling that person’s e-mail (called a mail server).
Usernames are typically a combination of the person’s first and last names and sometimes include periods, underscores, and numbers, but cannot include blank spaces. To ensure a unique e-mail address for everyone in the world, usernames must be unique within each domain name.
It is up to each organization with a registered domain name to ensure that one—and only one—exact
same username is assigned to its domain.
>E-mail address. An Internet address consisting of a username and computer domain name that uniquely identifies a person on the Internet.
>Username. A name that uniquely identifies a user on a specific computer network.