Transcript Tutorial 6

XP
Tutorial 6
Downloading and Storing Data
Using FTP and Other Services to
Transfer and Store Data
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Objectives
• Learn what FTP is and how it works.
• Explore how to use an FTP client program and Web
browser to transfer files.
• Navigate an FTP site using a Web browser.
• Learn how to compress and decompress files and to
check them for viruses.
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Objectives
• Download an FTP client program using a Web
browser.
• Download a compression program using an FTP
client program.
• Install and use a compression program.
• Trace the connection between your computer and a
remote computer.
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Objectives
• Explore storage options on the Internet.
• Learn about emerging technologies for collaborative
authoring on the Web.
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Understanding
File Transfer Protocol
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• FTP, or File Transfer Protocol, is the Internet
protocol that transfers files between computers that
are connected to the Internet.
• The site to which you are sending files and from
which you are receiving files is called an FTP site,
FTP server, or a remote computer.
• When you use your computer to connect to an FTP
site, it is called the local computer.
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Understanding
File Transfer Protocol
• When you send a file using FTP, you upload the file to send it
from your computer to the FTP site.
• When you receive a file, you download the file from the FTP
site and receive it on your computer.
• You connect to a remote computer and request it to either
receive files from your computer or transfer files to your
computer.
• FTP seamlessly transfers files between different operating
systems.
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File Transfer Modes
• You can select one of two file transfer modes—ASCII or
binary—that you want to use before transferring the file.
• ASCII text contains symbols typed from the keyboard but
does not include any nonprintable, binary codes.
• Many files such as pictures, movies, sound files, and
graphics are binary.
• Choose ASCII mode to transfer plain-text files.
• Choose binary mode for transferring everything else.
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File Types and Extensions
• The decision to transfer a file using binary or ASCII mode is
largely determined by noting the file’s type. The file type can be
determined by its extension.
• A file extension is the last three characters following the period
in the filename.
• You can download files with a file extension of .txt in ASCII
mode.
• You should download files with other file extensions (.doc, .xls,
etc.) in binary mode.
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File Types and Extensions
Filename &
Extension
Transfer
Extension
Mode
Type of file
picture.bmp
.bmp
Binary
Microsoft Paint
readme.doc
.doc
Binary
Word document
spinner.exe
.exe
Binary
Executable program
starship.gif
.gif
Binary
Picture
index.html or
index.htm
.html or
.htm
ASCII
HTML document
(Web Page)
chapter1.zip
.zip
Binary
Compressed file
readme.txt
.txt
ASCII
Text file
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Connecting to an FTP Server
• To transfer files between your computer and a remote
computer, you must first connect to the remote
computer.
• You can connect to a remote computer by logging on
to it using an FTP client program or your Web
browser.
• Some FTP client programs and browsers will select
the file transfer mode of binary or ASCII
automatically.
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FTP Using an FTP
Client Program
• An FTP client program resides on your PC and
transfers files between your computer and an FTP
site.
• Most FTP client programs have menu bars or
toolbars to help you execute commands.
• FTP client programs transfer files quickly and provide
features that let you resume downloading a file when
your connection is lost or interrupted.
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FTP Using an FTP
Client Program
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FTP Using an FTP
Client Program
• When selecting an FTP client program, choose one
that supports all or most of the following desirable
features:
 Multipane display showing both the local & remote
computer directories.
 Allows you to transfer multiple files in one FTP
session.
 Permits drag and drop file transfers.
 Simplifies the process of deleting directories on
local and remote computers.
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FTP Using an FTP
Client Program
• Desirable features (continued):
 Allows you to transfer selected files unattended.
 Recovers interrupted file transfers by continuing
the transfer process from the point of interruption.
 Reconnects automatically to sites that disconnect
a transfer when your connection exceeds the
maximum allotted time.
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FTP Using a Web Browser
• Most Web browsers, including Microsoft Internet Explorer
and Netscape Navigator, support FTP, but have limited
functionality when compared to FTP client programs.
• To upload a file, you must drag it from your desktop or
Windows Explorer and drop it in the correct location in the
browser window.
• To download a file, you select the file to download and tell
the browser where to save it on your computer.
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FTP Using a Web Browser
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Levels of Access for FTP Servers
• To use a remote computer, you must identify
yourself, or log on, by supplying your user name and
password.
• Public access: anyone can connect to the FTP site.
Access is restricted to only those files and folders
designated for access by public users.
• Restricted access: do not allow public visitors.
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Anonymous FTP
• Anonymous login: logging on to one of the many
publicly accessible, remote computers connected to
the Internet.
• You use anonymous as your user name.
• Anonymous FTP session: when you download or
upload files using an anonymous login.
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Anonymous FTP
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Anonymous FTP
• Public FTP sites usually impose limits on uploading files or
provide only one publicly accessible directory to which you
can upload files.
• Access to selected files and directories is also limited.
• You should obey all rules and regulations regarding
anonymous access.
• Look for the site’s acceptable use rules and policies in the
readme.txt file in the pub (public) directory.
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Full-Privilege FTP
• Full-privilege FTP: an FTP site that is not public
and requires a user name and password to access its
content.
• The system might automatically direct you to a
particular directory on the FTP site in which you have
been given rights to upload and download files.
• You can usually store files for longer periods than you
can on a public FTP site.
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Using a Public Directory
• Public directory (pub): the directory that some
public FTP sites allow users with anonymous FTP
access to view.
• Webmaster: the title given to the manager of a
website.
• The webmaster must monitor the files uploaded to a
public directory on a regular basis to check for
viruses and to find and delete any illegally uploaded
files.
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Using a Web Browser
to Navigate an FTP Site
• FTP sites are organized hierarchically, much like
the folders and files on a computer’s hard drive.
• When you access an FTP site, you usually enter at
the site’s root directory.
• Most sites prevent users with anonymous logins from
accessing some files and directories in the root
directory.
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Using a Web Browser
to Navigate an FTP Site
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Using a Web Browser
to Navigate an FTP Site
• An FTP site usually stores directories (folders) and
files.
• Double-clicking a file either opens the file in a new
browser window or in a program window so you can
view the file, or it begins downloading the file to your
computer.
• Double-clicking a folder opens the folder and displays
its contents.
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Using a Web Browser
to Navigate an FTP Site
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Checking Files for Viruses
• Computer viruses pose a real and potentially costly
threat to anyone using the Internet.
• Computer viruses are programs that “infect” your
computer and cause harm to your disk or programs.
• You must know how to detect and eradicate viruses if
you plan to download anything, including data,
programs, or e-mail attachments.
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Checking Files for Viruses
• Virus detection software, also called antivirus software,
regularly scans the files on your computer and files being
downloaded to your computer.
• Files are compared to a signature that known viruses carry.
• A virus signature (also called a virus pattern or a virus
definition) is a sequence (string) of characters that is always
present in a particular virus.
• When the virus detection program finds a virus signature, it
warns you. You can either delete the file or ask the virus
detection program to remove the virus.
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Checking Files for Viruses
• Two popular choices for protecting PCs are Norton AntiVirus
and McAfee VirusScan.
• Antivirus software must be turned on, properly configured, and
include current virus patterns to protect your computer from
viruses.
• You must regularly download virus patterns from the server to
keep your computer safe.
• One of the best ways to protect your computer from viruses is to
be careful about which files you download and the sources you
use to get those files.
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Checking Files for Viruses
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Visiting and Using a
Download Site
• A good way of locating software on the Internet is to
use one or more Internet search engines.
• Several Web sites provide links to freeware and
shareware programs. Some of these same sites also
allow you to download programs directly.
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Downloading Programs
• Freeware: software that is available to users at no cost and
with no restrictions.
• Users must accept the implicit or explicit warning that the
software might contain bugs.
• Bugs: errors sometimes contained in freeware due to limited
testing of the software.
• A lot of good-quality commercial software started as freeware.
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Downloading Programs
• Shareware: similar to freeware, but it is usually available for
free during a short evaluation period.
• After the evaluation expires, shareware stops functioning.
• Users are expected to stop using the shareware after the
specified initial trial period and uninstall it from their computers.
• Anyone who likes the program and wants to continue using it
can purchase a license.
• Shareware is usually more reliable than freeware because the
shareware developer is sometimes willing to accept
responsibility for the program’s operation.
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Downloading Programs
•
There are three popular ways to turn shareware
users into paying customers:
 Build a counter into the program
 Insert an internal date checker
 Use a “nag” screen that appears each time you
start the program
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Downloading Programs
 Limited Edition (LE) or Evaluation Version: a restricted
version of a shareware program.
 Provides most of the functionality of the full version that is
for sale.
 Omits one or more useful features of the full version.
 You can sometimes download a limited edition
version and use it for free.
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Using a Web Browser to XP
Download an FTP Client Program
• The time it takes to transfer the program files varies based on
the speed of your Internet connection and the amount of traffic
at the FTP site.
• If you encounter problems while downloading a file, stop the
process by clicking the Cancel button and try again later.
• After downloading anything from the Internet, your first priority is
to scan the file for viruses.
• After installing any program, you can delete the downloaded
files from the drive and folder to which you downloaded it, or you
can keep it in case you need to reinstall the program.
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Using a Web Browser to XP
Download an FTP Client Program
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Using an FTP Client
to Download WinZip
• File compression programs compress files to
decrease the amount of space they require and also
to decrease the time it takes to upload and download
files.
• WinZip is a popular file compression program which
is available for free during its evaluation period.
• When you use an FTP client program to save a site’s
address and your user name and password, you are
creating an FTP session profile.
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Using an FTP Client
to Download WinZip
• Log on to the remote computer by supplying its URL, your user
name or anonymous, and your password.
• Navigate to the file you want to download.
• Click the filename on the remote computer to select it.
• If necessary, select binary or ASCII transmission mode.
• Execute the command that downloads the file from the FTP site
to your computer and end the FTP session by disconnecting
from the remote computer.
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Compressing and
Decompressing Files
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• Internet files of all types are frequently stored in compressed
form.
• Compressed files use less space when stored and they take
less time to be transferred from one computer to another.
• You can use a file compression program to decrease the
original size of most files.
• After you download a compressed file, you must use a
program to restore the file to its original state before you can
open or execute it.
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Compressing and
Decompressing Files
• The process of restoring a compressed file to its original state is
called file decompression, or file expansion.
• FTP recognizes most compressed files by their extensions.
• The most common extension is .zip, which is why some people
refer to compressed files as zip files or a zip archive.
• If you download a compressed file, you must have a file
compression program installed on your computer to view its
contents.
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Compressing and
Decompressing Files
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Tracing an Internet Route
• Mirror site: a replica of an existing server that provides an
alternate location for downloading files.
• The distance between your PC and a remote computer on the
Internet is measured in hops.
• Hop: a connection between two connections.
• You can count the hops and identify the computers between
your PC and a remote computer using the Windows tracert (for
trace route) program.
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Tracing an Internet Route
• You can use the tracert program to make an
informed choice when selecting a download site.
• Tracert will show you up to 30 hops and indicate the
response time, the site name, and the IP address of
each hop along the route.
• Ping (Packet Internet Groper): a program that tests
a computer to determine if it is connected to the
Internet.
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Using Online Storage Services
• When you use an ISP for your Internet connection and e-mail
services, you might also receive some free space to use to store
a Web site or files.
• Many services have evolved to meet the increased need for
ways to store and share files. FTP sites are one way of sharing
and storing files.
• ISPs and other entities have started providing three or more
megabytes of storage space on their servers, either free or for a
fee, creating a new business model.
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Tracing an Internet Route
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Using Online Storage Services
• Users access the online storage space using an FTP
client program, a program or other interface provided by
the provider, or a Web browser.
• The space is secured with an account name and
password and permits the sharing of files by many users.
• Many businesses rely on online storage services to send
and receive large files while employees are traveling or as
a normal course of business.
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Using Online Storage Services
• Many individuals use online storage services to store computer
backup files, collections of sound files, personal Web sites, and
other data.
• As a result of bandwidth problems, many online storage
providers have changed their policies to limit the number of
transfers and amount of space provided, to charge a small
monthly fee for use of the space, or a combination of both.
• Some online storage providers come and go on a regular basis
so it is important to backup important files and keep a copy of
them locally.
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Online Storage Providers
• Some popular online storage
providers are:
 Xdrive Technologies
 My Docs Online
 Yahoo! Briefcase
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Collaborative Authoring
on the Web
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• Using the Internet to collaborate on files has been discussed
since the first Web browser was created in 1994.
• Collaboration: a method for multiple developers or authors to
work on the same file without having to download it, edit it, and
transfer it back to the original author(s).
• The desire for transferring and editing files over the Internet
using the HTTP protocol led to a new protocol for the Internet
known as WebDAV.
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Collaborative Authoring
on the Web
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• WebDAV (DAV): Web Distributed Authoring and
Versioning is a standard extension of the original HTTP
1.1 protocol that is used to transfer Web pages over the
Internet.
• Because HTTP has built-in features that provide security
and other desirable features during file transfers, it
provides collaboration features on the Internet.
• WebDAV Working Group: the group of individuals who
are actively collaborating on defining this new protocol.
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Collaborative Authoring
on the Web
• The WebDAV Working Group is dedicated to developing and
improving the WebDAV protocol on the Internet to create an
operating-system neutral form of collaborative authoring.
• Internet Engineering Task Force (IETF): a large group of
individuals who contribute to the evolution of new and existing
Internet technologies.
• Four important features that make the WebDAV protocol
desirable are file locking, properties, name space management,
and collections.
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Collaborative Authoring
on the Web
•
WebDAV is available today with some limitations. The Web Publishing
Wizard, which is part of the Windows XP operating system, lets you
transfer files directly to an Internet server using the HTTP protocol.
•
Windows refers to WebDAV as “Web folders.”
•
To download a file using Windows XP and the HTTP protocol with
WebDAV, you can create a network place, which is a shortcut to a Web
site, FTP site, network location, or online storage provider.
•
After creating the network place, you can download, upload, and share
files at the network location you defined.
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Summary
• You can use a Web browser and an FTP client
program to transfer files between computers
connected to the Internet.
• You can use a download site to evaluate freeware,
shareware, limited edition, and full use programs
based on your needs.
• You can use online storage providers to store files
that you can share with other users.
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