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Email
Electronic mail, often abbreviated to
e-mail, email or eMail, is any method
of creating, transmitting, or storing primarily
text-based human communications with digital
communications systems. Historically, a variety of
electronic mail system designs evolved that were often
incompatible or not interoperable. With the
proliferation of the
Internet since the early 1980s, however, the
standardization efforts of Internet architects succeeded
in promulgating a single standard based on the
Simple Mail Transfer Protocol (SMTP), first
published as Internet Standard 10 (RFC
821) in 1982.
Modern e-mail systems are based on a
store-and-forward model in which e-mail computer
server systems, accept, forward, or store messages on
behalf of users, who only connect to the e-mail
infrastructure with their personal computer or other
network-enabled device for the duration of message
transmission or retrieval to or from their designated
server. Rarely is e-mail transmitted directly from one
user's device to another's.
While, originally, e-mail consisted only of text
messages composed in the
ASCII character set, virtually any media format can
be sent today, including attachments of audio and video
clips.
[edit]
Spelling
The
spellings e-mail and email are both
common. Several prominent journalistic and technical
style guides recommend e-mail,[1][2][3][4]
and the spelling email is also recognized in many
dictionaries.[5][6][7][8][9]
In the original
RFC neither spelling is used; the service is
referred to as mail, and a single piece of
electronic mail is called a message.[10][11][12]
Newer RFCs and
IETF working groups require email for
consistent capitalization, hyphenation, and spelling of
terms[13].
ARPAnet/DARPAnet
users and early developers from
Unix,
CMS,
AppleLink,
eWorld,
AOL,
GEnie, and
HotMail used eMail with the letter M
capitalized. The authors of some of the original RFCs
used eMail when giving their own addresses.[11][12]
Donald Knuth considers the spelling "e-mail" to be
archaic, and notes that it is more often spelled "email"
in the UK. In other European languages the word "email"
has a complete different meaning: "enamel".[14]
[edit]
Origin
E-mail predates the inception of the
Internet, and was in fact a crucial tool in creating
the Internet.
MIT first demonstrated the
Compatible Time-Sharing System (CTSS) in 1961.[15]
It allowed multiple users to log into the
IBM 7094[16]
from remote dial-up terminals, and to store files online
on disk. This new ability encouraged users to share
information in new ways. E-mail started in 1965 as a way
for multiple users of a
time-sharing
mainframe computer to communicate.
The Internet is a global system of
interconnected
computer networks that interchange
data by
packet switching using the standardized
Internet Protocol Suite (TCP/IP). It is a "network
of networks" that consists of millions of private and
public, academic, business, and government networks of
local to
global scope that are linked by
copper wires,
fiber-optic cables,
wireless connections, and other technologies.
The Internet carries various
information resources and services, such as
electronic mail,
online chat,
file transfer and
file sharing,
online gaming, and the inter-linked
hypertext documents and other resources of the
World Wide Web (WWW).
Terminology
The terms Internet and World Wide Web
are often used in every-day speech without much
distinction. However, the Internet and the
World Wide Web are not one and the same. The
Internet is a global data communications system. It is a
hardware and software infrastructure that provides
connectivity between
computers. In contrast, the Web is one of the
services communicated via the Internet. It is a
collection of interconnected documents and other
resources, linked by
hyperlinks and
URLs.[1]
History
-
Creation
A 1946 comic
science-fiction story,
A Logic Named Joe, by
Murray Leinster laid out the Internet and many of
its strengths and weaknesses. However, it took more than
a decade before reality began to catch up with this
vision.
The
USSR's launch of
Sputnik spurred the United States to create the
Advanced Research Projects Agency, known as ARPA, in
February
1958 to regain a technological lead.[2][3]
ARPA created the
Information Processing Technology Office (IPTO) to
further the research of the
Semi Automatic Ground Environment (SAGE) program,
which had networked country-wide
radar systems together for the first time.
J. C. R. Licklider was selected to head the IPTO,
and saw universal networking as a potential unifying
human revolution.
Licklider moved from the Psycho-Acoustic Laboratory
at
Harvard University to
MIT in
1950, after becoming interested in
information technology. At MIT, he served on a
committee that established
Lincoln Laboratory and worked on the SAGE project.
In
1957 he became a Vice President at
BBN, where he bought the first production
PDP-1 computer and conducted the first public
demonstration of
time-sharing.
At the IPTO, Licklider recruited
Lawrence Roberts to head a project to implement a
network, and Roberts based the technology on the work of
Paul Baran,[citation
needed] who had written an
exhaustive study for the
U.S. Air Force that recommended
packet switching (as opposed to
circuit switching) to make a network highly robust
and survivable. After much work, the first two nodes of
what would become the
ARPANET were interconnected between
UCLA and
SRI International in
Menlo Park, California, on October 29, 1969.
A computer network is a group of
interconnected
computers. Networks may be classified according to a
wide variety of characteristics. This article provides a
general overview of some types and categories and also
presents the basic components of a network.
[edit]
Introduction to Computer
Networks
A network is a collection of computers connected to
each other. The network allows computers to communicate
with each other and share resources and information. The
Advance Research Projects Agency (ARPA) designed
"Advanced Research Projects Agency Network" (ARPANET)
for the United States Department of Defense. It was the
first computer network in the world in late 1960's and
early 1970's.[citation
needed]
[edit]
Network Classification
The following list presents categories used for
classifying networks.
Based on their scale, networks can be classified as
Local Area Network
(LAN), Wide Area Network
(WAN), Metropolitan Area Network
(MAN), Personal Area Network
(PAN),Virtual Private Network
(VPN) etc.
[edit]
Connection method
Computer networks can also be classified according to
the hardware and software technology that is used to
interconnect the individual devices in the network, such
as
Optical fiber,
Ethernet,
Wireless LAN,
HomePNA, or
Power line communication.
Ethernet uses physical wiring to connect devices.
Frequently deployed devices include hubs, switches,
bridges and/or routers.
Wireless LAN technology is designed to connect
devices without wiring. These devices use
radio waves or
infrared signals as a transmission medium.
[edit]
Functional relationship
(Network Architectures)
Computer networks may be classified according to the
functional relationships which exist among the elements
of the network, e.g.,
Active Networking,
Client-server and
Peer-to-peer (workgroup) architecture.
[edit]
Network topology
-
Computer networks may be classified according to the
network topology upon which the network is based,
such as
Bus network,
Star network,
Ring network,
Mesh network,
Star-bus network,
Tree or Hierarchical topology network. Network
Topology signifies the way in which devices in the
network see their logical relations to one another. The
use of the term "logical" here is significant. That is,
network topology is independent of the "physical" layout
of the network.
A computer is a
machine that manipulates
data according to a list of
instructions.
The first devices that resemble modern computers date
to the mid-20th century (1940–1945), although the
computer concept and various machines similar to
computers existed earlier. Early electronic computers
were the size of a large room, consuming as much power
as several hundred modern personal computers (PC).[1]
Modern computers are based on tiny
integrated circuits and are millions to billions of
times more capable while occupying a fraction of the
space.[2]
Today, simple computers may be made small enough to fit
into a
wristwatch and be powered from a
watch battery.
Personal computers, in various forms, are
icons of the
Information Age and are what most people think of as
"a computer"; however, the most common form of computer
in use today is the
embedded computer. Embedded computers are small,
simple devices that are used to control other devices —
for example, they may be found in machines ranging from
fighter aircraft to
industrial robots,
digital cameras, and
children's toys.
The ability to store and execute lists of
instructions called
programs makes computers extremely versatile and
distinguishes them from
calculators. The
Church–Turing thesis is a mathematical statement of
this versatility: any computer with a certain minimum
capability is, in principle, capable of performing the
same tasks that any other computer can perform.
Therefore, computers with capability and complexity
ranging from that of a
personal digital assistant to a
supercomputer are all able to perform the same
computational tasks given enough time and storage
capacity.
History of computing
-
It is difficult to identify any one device as the
earliest computer, partly because the term "computer"
has been subject to varying interpretations over time.
Originally, the term "computer" referred to a person who
performed numerical calculations (a
human computer), often with the aid of a
mechanical calculating device.
The history of the modern computer begins with two
separate technologies - that of automated calculation
and that of programmability.
Examples of early mechanical calculating devices
included the
abacus, the
slide rule and arguably the
astrolabe and the
Antikythera mechanism (which dates from about
150-100 BC).
Hero of Alexandria (c. 10–70 AD) built a mechanical
theater which performed a play lasting 10 minutes and
was operated by a complex system of ropes and drums that
might be considered to be a means of deciding which
parts of the mechanism performed which actions and when.[3]
This is the essence of programmability.
The "castle clock", an
astronomical clock invented by
Al-Jazari in 1206, is considered to be the earliest
programmable
analog computer.[4]
It displayed the
zodiac, the
solar and
lunar orbits, a
crescent moon-shaped
pointer travelling across a gateway causing
automatic doors to open every
hour,[5][6]
and five
robotic musicians who play music when struck by
levers operated by a
camshaft attached to a
water wheel. The length of
day and
night could be re-programmed every day in order to
account for the changing lengths of day and night
throughout the year.[4]
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