Transcript Internet Adapted 11

Tutorial 11
Special Adapted
Downloading and
Storing Data
Objectives
XP
• Learn what FTP is and how it works
• Explore how to use a Web browser to transfer
files
• Navigate an FTP site using a Web browser
• Learn about checking downloaded files for
viruses and other threats
• Learn about types of download software
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Objectives
XP
• Evaluate download software for appropriateness
and quality
• Download an FTP client program using a Web
browser
• Download a compression program using an FTP
client program
• Learn how to compress and decompress files
• Explore storage options on the Internet
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Understanding
File Transfer Protocol
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• FTP (File Transfer Protocol): the Internet
protocol that transfers files between computers
connected to the Internet
• FTP site (FTP server, remote computer, or
remote site): the site you are sending files to and
receiving files from
• Local computer or local site: your computer
when you use it to connect to an FTP site
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Understanding
File Transfer Protocol
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• When you send a file using FTP, you upload the
file to send it from your computer to the remote
site
• When you receive a file, you download the file
from the remote site to your computer
• FTP seamlessly transfers files between different
operating systems
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File Transfer Modes
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• You can select one of two file transfer modes:
– ASCII text: contains symbols typed from the
keyboard but does not include any nonprintable,
binary codes
– Binary: files such as pictures, movies, sound files, and
graphics
• Choose ASCII mode to transfer plain-text files
• Choose binary mode for transferring everything
else
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File Types and Extensions
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• File extension: the characters following the
period in the filename
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Logging on to an FTP Site Using a
Web Browser
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• Most Web browsers, including Internet Explorer
and Firefox, 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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Logging on to an FTP Site Using a
Web Browser
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Anonymous FTP
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• To use a remote computer, you must identify
yourself, or log on, by supplying your user name
and password
• 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
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• 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
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• Full-privilege FTP: FTP site access that requires a
user name and password
• 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
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• Public directory (pub): the directory that some
public FTP sites allow users with anonymous FTP
access to view
• Webmaster:
– Title given to the manager of a website
– 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
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• 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
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• An FTP site usually stores directories (folders) and
files
• Clicking a link to a directory opens the folder and
displays its contents
• Clicking the link to a filename opens the file and
displays its contents
• To download a file to your computer, right-click the
filename to open the shortcut menu, click Save
Target As, navigate to the drive and folder in which
to save the file, and then click the Save button
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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
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Checking Files for Viruses
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• Computer viruses are programs that “infect”
your computer and cause harm to your disk or
programs
• Viruses pose a real and potentially costly threat
to anyone using the Internet
• You must know how to detect and eradicate
viruses if you plan to download anything,
including data, programs, instant messages, or
email attachments
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Checking Files for Viruses
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• Antivirus program:
– Regularly scans the files on your computer and files being
downloaded to your computer
– Files are compared to a signature that known viruses carry
– Virus signature (virus pattern or virus definition): a sequence
(string) of characters that is always present in a particular
virus
• When the antivirus program finds a virus
signature, it warns you. You can either delete the
file or ask the antivirus program to remove the
virus
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Checking Files for Viruses
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• Three popular choices for protecting PCs are produced
by Symantec (Norton), McAfee, and ZoneAlarm
• 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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Types of Download Software
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• Many programs are available for download at
little or no cost
• 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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Types of Download Software
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• Freeware: software available to users at no cost
and with no restrictions
• Bugs: errors sometimes contained in freeware
due to limited testing of the software
• Users must accept the implicit or explicit warning
that the software might contain bugs
• A lot of good-quality commercial software
started as freeware
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Types of Download Software
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• Shareware:
– Similar to freeware, but it is usually available for free during a
short evaluation period
– After the evaluation expires, it stops functioning
– Users are expected to stop using it 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
– Usually more reliable than freeware because the shareware
developer is sometimes willing to accept responsibility for the
program’s operation
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Types of Download Software
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• Limited Edition (LE) or Evaluation Version:
– Restricted version of a 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
Using a Web Browser to
Download an FTP Client Program
XP
• Start your Web browser, and then open the Web site
from which you will download the file
• Navigate to the page that contains the file you want to
download, and then click the link to the file
• In Internet Explorer, click the Save button in the File
Download dialog box, click the Browse Folders link (if
necessary), navigate to the drive or folder in which to
store the file, and then click the Save button If
necessary, click the Close button to close the dialog box
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Using a Web Browser to
Download an FTP Client Program
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• In Firefox, click the Save File button to download the
file. Select the location in which to save the file (if
available), click the Save it to disk option button (if
necessary), and then click the OK button. Navigate to
the drive or folder in which to store the file, and then
click the Save button. Close the dialog box (if
necessary). If the file is downloaded automatically to an
existing folder or to the desktop, Close the Downloads
dialog box, locate the file, and then cut and paste it to
the drive and folder in which to store the file
Using a Web Browser to
Download an FTP Client Program
XP
• The time it takes to transfer the program files
varies based on the speed of your Internet
connection and the file’s size
• 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 security
threats
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Using an FTP Program
to Download WinZip
XP
• 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
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Using an FTP Program
to Download WinZip
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• Log on to the remote site by supplying its URL, your user
name or anonymous, and your password (if necessary)
• Navigate to the file you want to download
• Click the filename on the remote site to select it
• Navigate to the drive or folder on your computer to
which to download the file
• Drag the file from the remote site to the drive or folder
on your computer
• End the FTP session by disconnecting from the remote
site
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Compressing and
Decompressing Files
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• Compressed files: use less space when stored and they
take less time to be transferred from one computer to
another
• File compression program: decreases 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
• The process of restoring a compressed file to its original
state is called file decompression or file expansion
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Compressing and
Decompressing Files
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• FTP recognizes most compressed files by their
extensions
• The most common extension for compressed
files 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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Compressing and
Decompressing Files
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Evaluating Online Storage Services
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• When you use an ISP for your Internet connection
and email 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
storage space on their servers, either free or for a
fee, creating a new business model
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Using Online Storage Services
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• 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 individuals use these online storage
services to store backup files, sound files,
personal Web sites, pictures, and other data
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Using Online Storage Services
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• 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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Using Online Storage Services
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Summary
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• You can:
– Use a Web browser and an FTP client program to
transfer files on the Internet
– Evaluate freeware, shareware, limited edition, and
licensed programs
– Use online storage providers to store files that you
can share with other users
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