Transcript BIT102-chapter_6(download) - E

Chapter 6: Downloading
and Storing Data
Prepared by: Ms Melinda Chung
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
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and a remote computer.
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

FTP (File Transfer Protocol) - the Internet protocol
that transfers files between computers that are
connected to the Internet

FTP site (FTP server, or a remote computer) - the
site to which you are sending files and from which
you are receiving files

Local computer - is the computer used to connect
to an FTP site
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Understanding
File Transfer Protocol

Uploading - when you send a file using FTP
from your computer to the FTP site

Downloading - when you receive a file from the
FTP site on your computer

FTP seamlessly transfers files between different
operating systems
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File Transfer Modes

ASCII or binary - file transfer modes use to transfer files

ASCII text - contains all keyboard symbols but excludes
nonprintable, binary codes

Binary files - pictures, movies, sound files, and graphics

Choose ASCII mode to transfer plain-text files

Choose binary mode to transfer other file types
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File Types and Extensions
Transfer
Filename &
Extension
Extension
Mode
Type of file
picture.bmp
.bmp
Binary
Microsoft Paint
readme.doc
spinner.exe
.doc
.exe
Binary
Binary
Word document
Executable program
starship.gif
.gif
Binary
Picture
index.html or
index.htm
chapter1.zip
.html or
.htm
.zip
ASCII
Binary
HTML document
(Web Page)
Compressed file
readme.txt
.txt
ASCII
Text file
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Connecting to an FTP Server

Connect to the remote computer for file transfer

Connect to a remote computer via a FTP client
program or a Web browser

FTP client programs and browsers select the file
transfer mode (binary or ASCII) automatically
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FTP Using an FTP
Client Program

An FTP client program - transfers files between your
computer and an FTP site

FTP client program - has menu bars or toolbars for
command execution

FTP client program - provides features that resume
downloading of a file when the connection is lost or
interrupted
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FTP Using an FTP
Client Program
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FTP Using a Web Browser

Web browsers support FTP with limited functionality

Upload a file - drag it from your desktop or Windows
Explorer and drop it in the correct location in the
browser window

Download a file - select the file to download and tell
the browser where to save it on the computer
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FTP Using a Web Browser
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Levels of Access for FTP
Servers

Access a remote computer: log on with your user
name and password

Public access: 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: to publicly accessible,
remote computers connected to the Internet

Use anonymous as your user name

Anonymous FTP session: for download or
upload files in an anonymous login session
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Anonymous FTP
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Anonymous FTP

Public FTP sites - impose limits on uploading files in
a publicly accessible directory

Limited access to selected files and directories

Obey all rules and regulations regarding
anonymous access

The acceptable use rules and policies are given in
the readme.txt file in the pub (public) directory
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Full-Privilege FTP

Full-privilege FTP: a non public FTP site that
requires a user name and password to access its
content

Privilege directory: for users having the rights to
upload and download files

Can store files for longer periods than on a public
FTP site
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Using a Public Directory

Public directory (pub): the directory of the
public FTP sites allow users with anonymous FTP
access to view

Webmaster: manager of a website

Webmaster: monitors the files uploaded to a
public directory on a regular basis
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Using a Web Browser
to Navigate an FTP Site

FTP sites are organized hierarchically

When you access an FTP site, you enter at the
site’s root directory

Most sites prevent users with anonymous logins
from accessing 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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Checking Files for Viruses

Computer viruses - a real and potentially costly
threat

Computer viruses - are programs that “infect” your
computer and cause harm to your disk or programs

Need to to detect and eradicate viruses in
downloading materials (including data, programs, or
e-mail attachments)
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Checking Files for Viruses

Virus detection software (antivirus software) - use to
scan 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

Delete the file or ask the virus detection program to
remove the virus if found
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Checking Files for Viruses

Two popular choices for protecting PCs are Norton
AntiVirus and McAfee VirusScan

Turn on the antivirus software to protect your computer from
viruses

Regularly download virus patterns from the server to keep
your computer safe

Be cautious about the files you download and the sources
you use to get those files
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Checking Files for Viruses
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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
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freeware
Downloading Programs

Shareware: similar to freeware, is available for free
during a short evaluation period

After the evaluation expires, shareware stops functioning

Expected to stop using the shareware after the specified
initial trial period and uninstall it from computers

Can purchase a license if wants to continue using the
program

Shareware is usually more reliable than freeware
because the shareware developer is willing to accept
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responsibility for the program’s operation
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
Download an FTP Client Program
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Using an FTP Client
to Download WinZip

Log on to the remote computer with your user name or
anonymous, and your password

Navigate & select the file you want to download, if
necessary, select the binary or ASCII transmission
mode filename

Execute the command to download the file from the
FTP site to your computer

FTP recognizes most compressed files by their
extensions
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Compressing and
Decompressing Files

File compression programs - compress files to decrease the
amount of space the time it takes to upload or download files

WinZip - a popular file compression program, free during its
evaluation period

Restore a compressed file before you can open or execute it

File decompression (file expansion) - the process of
restoring a compressed file to its original state

.zip file extension - for compressed files
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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

Hop: a connection between two connections

Hops: measure the distance between your PC and a
remote computer on the Internet

Windows tracert (for trace route) program - to count
the hops and identify the computers between a PC and
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a remote computer
Tracing an Internet Route

Tracert: shows up to 30 hops and indicates 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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Tracing an Internet Route
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Using Online Storage Services

ISPs and other entities have started providing storage
space on their servers (either free or for a fee), creating
a new business model

FTP sites are one way of sharing and storing files - to
meet the increased need for ways to store and share
files

Access the online storage space using a FTP client
program or other interface provided by the provider, or a
Web browser
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Using Online Storage Services

The space is secured with an account name and
password and permits the sharing of files by many
users

Businesses & employees rely on online storage
services to send and receive large files

Individuals use online storage services to store
computer backup files, collections of sound files,
personal Web sites, and other data
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Using Online Storage Services

Bandwidth problems - some providers charge a
small monthly fee for use of the space online
storage

Important to backup - some online storage
providers come and go on a regular basis
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Online Storage Providers

Some popular online
storage providers are:



Xdrive Technologies
My Docs Online
Yahoo! Briefcase
links for
learning
about xdrive
services and
features
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Collaborative Authoring
on the Web

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)

WebDAV (Web Distributed Authoring and
Versioning): a new protocol for transferring and editing
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files using the HTTP protocol
Collaborative Authoring
on the Web

WebDAV: a standard extension of the original HTTP 1.1
protocol

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: to develop and improve
the WebDAV protocol and to create an operatingsystem 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: file locking, properties, name space
management, and collections
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Collaborative Authoring
on the Web

WebDAV’s application - the Web Publishing Wizard (part of
the Windows XP operating system), allows transfer files
directly to an Internet server using the HTTP protocol

Windows refers to WebDAV as “Web folders.”

Create a network place - a shortcut to a Web site, FTP site,
network location, or online storage provider using Windows
XP and the HTTP protocol with WebDAV

Download, upload, and share files - at the defined network
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location
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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