A download refers to the process of retrieving data
from a remote source. The most common type of download is someone
accessing a file from a server on the Internet;
but downloading does not exclusively refer to files retrieved from
the Internet. On the Internet, the most common servers
to download data from are an:
- Email server
- FTP server
- Web server
Each of these servers use a different Internet protocol, and each
of these protocols are a part of the Internet protocol suite. For
example, web servers will use HTTP (protocol), email servers will
use POP and SMTP (protocols), and ftp servers will use FTP (protocol).
Each of these protocols, which are used to download data across
the Internet, are part of the application layer of the Internet
protocol suite. These protocols will work in tandem with other protocols
within the Internet protocol suite: most notable TCP (protocol).
Downloading from the Internet is based upon a client-server model.
Which means a client program will request data from a server using
one of the protocols highlighted above. Web browsers are an example
of a client platform; which use HTTP to download webpages from web
servers. Email client programs, like Outlook Express, use POP and
SMTP to download email messages from mail servers.
Downloading data is an integral part of the Internet and the World
Wide Web. When users surf the World Wide Web, they are continually
downloading data stored on Web servers: html files, image files,
video files and sound files. The first ever web server was a 'NeXT'
computer; connected to the Internet by Tim Berners-Lee (the inventor
of the Web).
Downloading data from FTP servers (File Transfer Protocol) predates
the World Wide Web. Client programs, like file sharing programs,
typically use FTP to enable their users to download and upload files.
Some of the most common files downloaded from FTP servers are: software
software updates, patches, multimedia files, pictures, podcasts
and text documents.
The speed at which a download can be made is dependent upon the
file server (where the file is stored) and the download speed of
the user's Internet connection. Downloads are usually recorded in
bits, bytes, kilobytes
An alternative to downloading is streaming
(via webcasts and other means). Streaming
enables users to access data (usually video) "on the fly";
without having to save it as file. This has the advantage of users
being able to view the content immediately - without having to download
the whole file and then view it - and also saves storage space.
Youtube is a prime example of a streaming
How to download
To download files, a user requires a client program to connect
to the servers which store the file and retrieve it to the client
program. Client programs usually have a specific purpose: for example,
a file transfer client, like WS_FTP, can transfer files to FTP and
web servers (they can upload/download files in ASCII
and Binary format). Whereas, an email
client program, like Outlook Express, will only retrieve email messages
from mail servers.
The most popular client program for downloading files from the
Internet is a web browser; which, as you would assume, downloads
files (webpages, images etc) from web servers using HTTP. Some web
browsers support a range of Internet protocols, and can download
files from file, email and web servers.
Downloading data using a web browser is extremely easy to do:
- Most websites include a download hyperlink (wish you simple
- Right click on a mouse and 'Save As' for pictures and hyperlinks.
- Use the 'file' menu in the browser and select 'Save As' from
The above image shows a typical browser menu; which appears when
a user right clicks (with a mouse) a hyperlink. The 'save target
as' allows user to download a range of files. Downloading files
is essential for making a backup of important
files. The primary task of a web browser is to browse web pages.
Download managers, within browsers, tend to be simplistic; if the
download fails, they cannot recover the download from the error
point. Users can, however, purchase a professional download manager,
which can pause and resume downloads, resume broken downloads, schedule
downloads and find mirror sites if the current download provider
File formats that are commonly downloaded
When you download software files, you may find that the file has
been compressed. File compression
saves space on servers. If you have downloaded a file which is compressed:
you will need an application which is capable of decompressing the
file. Winzip is a prime example of such an application: which can
decompress (unzip) the zip
file format. Zip is the most popular type of file compression. Compressed
files are sometimes referred to as an archive
file; due to it including numerous files compressed into one file.
Some other popular file formats, and their corresponding file extension:
- avi - file format that supports video
and sound files.
- doc - formatted text file.
- pdf - portable document format; format developed by adobe systems.
- bin - macintosh binary II encoded file.
- exe - this is an executable file.
- gif - this is a image file format.
- gz/gzip - the gnu project's compression format.
- jar - compressed file type, which
is similar to the .zip file extension.
- jpg - this is a image file format.
- lwp - this program extension is for lotus
- mpg - file format that supports video
and sound files.
- mp3 - file compression for audio files.
- sea - macintosh self-extracting archive file.
- wav - waveform audio file format, designed
by microsoft and ibm.