Page 297 - DCAP101_BASIC_COMPUTER_SKILLS

Basic Computer Skills

Notes using more efficient computer programs for Web servers, etc.;

using other workarounds, especially if dynamic content is involved.
14.1.8 Market Structure

Market share of major Web servers For more details on HTTP server programs, see
Category:Web server software.
Below is the most recent statistics of the market share of the top web servers on the internet
by Netcraft survey in November 2010.

Vendor Product Web Sites Hosted Percent

Apache Apache 148,085,963 59.36%
Microsoft IIS 56,637,980 22.70%
Igor Sysoev nginx 15,058,114 6.04%
Google GWS 14,827,157 5.94%

lighttpd lighttpd 2,070,300 0.83%

14.2 E-mail

Electronic mail, commonly called email, e-mail or e.mail, is a method of exchanging digital
messages from an author to one or more recipients. Modern email operates across the
Internet or other computer networks. Some early email systems required that the author and
the recipient both be online at the same time, a la instant messaging. Today’s email systems
are based on a store-and-forward model. Email servers accept, forward, deliver and store
messages. Neither the users nor their computers are required to be online simultaneously;
they need connect only briefly, typically to an email server, for as long as it takes to send
or receive messages.
An email message consists of three components, the message envelope, the message header,
and the message body. The message header contains control information, including, minimally,
an originator’s email address and one or more recipient addresses. Usually descriptive
information is also added, such as a subject header field and a message submission date/
time stamp.

Originally a text only (7 bit ASCII and others) 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 a basic text message 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.

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