Email
From Wikipedia, the free encyclopedia
Electronic mail, commonly called
email or
e-mail, is a method of exchanging
digital messages across the
Internet or other
computer networks. Originally, email was transmitted directly from one user to another
computer. This required both computers to be
online at the same time, a la
instant messenger. Today's email systems are based on a
store-and-forward model. Email
servers accept, forward, deliver and store messages. Users no longer need be online simultaneously and need only connect briefly, typically to an
email server, for as long as it takes to send or receive messages.
An email message consists of two components, the message
header, and the message
body, which is the email's content. The message header contains control information, including, minimally, an originator's
email address and one or more recipient addresses. Usually additional information is added, such as a subject header field.
Originally a text-only communications medium, email was extended to carry multi-media content attachments, a process standardized in
RFC 2045 through 2049. Collectively, these RFCs have come to be called
Multipurpose Internet Mail Extensions (MIME).
The history of modern, global Internet email services reaches back to the early
ARPANET. Standards for encoding email messages were proposed as early as 1973 (
RFC 561). Conversion from ARPANET to the Internet in the early 1980s produced the core of the current services. An email sent in the early 1970s looks quite similar to one sent on the Internet today.
Network-based email was initially exchanged on the ARPANET in extensions to the
File Transfer Protocol (FTP), but is now carried by the
Simple Mail Transfer Protocol (SMTP), first published as
Internet standard 10 (
RFC 821) in 1982. In the process of transporting email messages between systems, SMTP communicates delivery parameters using a message
envelope separate from the message (header and body) itself.
Therapy
From Wikipedia, the free encyclopedia
Therapy (in
Greek:
????????), or
treatment, is the attempted remediation of a health problem, usually following a
diagnosis. In the medical field, it is synonymous with the word "treatment". Among psychologists, the term may refer specifically to
psychotherapy or "talk therapy".
Preventive therapy or
prophylactic therapy is a treatment that is intended to prevent a medical condition from occurring. For example, many
vaccines prevent infectious diseases. An
abortive therapy is a treatment that is intended to stop a medical condition from progressing any further. A medication taken at the earliest signs of a disease, such as at the very symptoms of a migraine headache, is an abortive therapy.
A
supportive therapy is one that does not treat or improve the underlying condition, but instead increases the patient's comfort.
[1] Supportive treatment may be
palliative care.
Contents
World Wide Web
The
World Wide Web, abbreviated as
WWW and commonly known as
the Web, is a
system of interlinked
hypertext documents accessed via the
Internet. With a
web browser, one can view
web pages that may contain
text,
images,
videos, and other
multimedia and navigate between them by using
hyperlinks. Using concepts from earlier hypertext systems,
English engineer and computer scientist
Sir Tim Berners-Lee, now the Director of the
World Wide Web Consortium, wrote a proposal in March 1989 for what would eventually become the World Wide Web.
[1] At
CERN in
Geneva,
Switzerland, Berners-Lee and Belgian computer scientist
Robert Cailliau proposed in 1990 to use "HyperText [...] to link and access information of various kinds as a web of nodes in which the user can browse at will",
[2] and publicly introduced the project in December.
[3]
"The World-Wide Web (W3) was developed to be a pool of human knowledge, and human culture, which would allow collaborators in remote sites to share their ideas and all aspects of a common project."
[4]
Internet
From Wikipedia, the free encyclopedia
Visualization of the various routes through a portion of the Internet. From 'The Opte Project'
The
Internet is a global system of interconnected
computer networks that use the standard
Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. It is a
network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic and optical networking technologies. The Internet carries a vast range of
information resources and services, such as the inter-linked
hypertext documents of the
World Wide Web (WWW) and the infrastructure to support
electronic mail.
Most traditional communications media including telephone, music, film, and television are being reshaped or redefined by the Internet. Newspaper, book and other print publishing are having to adapt to
Web sites and
blogging. The Internet has enabled or accelerated new forms of human interactions through
instant messaging,
Internet forums, and
social networking.
Online shopping has boomed both for major retail outlets and small
artisans and traders.
Business-to-business and
financial services on the Internet affect
supply chains across entire industries.
The origins of the Internet reach back to the 1960s with both private and United States military research into robust, fault-tolerant, and distributed computer networks. The funding of a new U.S.
backbone by the
National Science Foundation, as well as private funding for other commercial backbones, led to worldwide participation in the development of new networking technologies, and the merger of many networks. The
commercialization of what was by then an international network in the mid 1990s resulted in its popularization and incorporation into virtually every aspect of modern human life. As of 2009, an estimated quarter of Earth's population used the services of the Internet.
The Internet has no centralized governance in either technological implementation or policies for access and usage; each constituent network sets its own standards. Only the overreaching definitions of the two principal
name spaces in the Internet, the
Internet Protocol address space and the
Domain Name System, are directed by a maintainer organization, the
Internet Corporation for Assigned Names and Numbers (ICANN). The technical underpinning and standardization of the core protocols (
IPv4 and
IPv6) is an activity of the
Internet Engineering Task Force (IETF), a non-profit organization of loosely affiliated international participants that anyone may associate with by contributing technical expertise.
The Web's historic logo designed by Robert Cailliau