18 Internet Services and Applications
Concept Map
1. B
2. I
3. F
4. J
5. C
6. H
7. G
8. A
9. D
10. E
Concept Checker
1. T
2. T
3. F
4. T
5. F
Multiple Choice Questions
1. D
2. D
3. A
4. B
5. C
6. A
7. B
8. D
9. B
10. B
11. B
12. C
Short Questions
1. (a) A web server contains a program that uses the HTTP for exchanging data on the
WWW. (2)
(b) The first component is a spider (or bot) which creates a search engine index. (2)
The second component is used to create a database of keywords read by the spider.
(2) The third component is the access program which handles the search
requests. (2)
2. Advantages:
•Webmail can be accessed with a web browser without special application
software. (1)
•Webmail users can access their e-mails anywhere through the Internet. (1)
Disadvantages:
•Webmail has a limited capacity and is inconvenient to save the e-mails into the user’s
hard disk.
•Users must stay online while they are reading or writing e-mails.
•The operation of webmail is slower than that of the traditional e-mail system.
(any two × 1)
3. (a) ‧Customers cannot inspect and try the goods before purchasing them.
‧Some goods or services are unable to be shipped by mail or by carrier.
‧The shipping cost and other financial charges may be too high when compared to
the price of the sold item.
(any two × 1)
(b) (i) Credit card payment service (1), online market research (1)
(ii) Online bookshop / online banking / online florist
(any two × 1)
(iii) Online auctions (1), online barter (1)
4. Packages and legal documents which require chops and signatures must be sent by
traditional mailing. (1)
Registered letters assure that they are received by the right persons. (1)
5. (a) Peter has to download the video file completely before he can play the video. (1)
But Mary can view the video file once a small portion of video is downloaded. (1)
This technology is called streaming. (1)
(b) For a slow Internet connection (1), video streaming can happen only when a large
portion of the video file have been downloaded (1) to ensure that the buffered video
data is enough to play smoothly. (1)
6. (a) • Compress the video files.
• Lower the frame rate of the video files.
• Lower the frame size of the video files.
(any two × 1)
(b) • E-mail
• Webmail
• Video conferencing
• Instant messaging programs
(any two × 1)
Long Questions
1. (a) Advantages:
•Allow for on-demand knowledge acquisition. (1)
•Provide consistent course delivery. (1)
•Modifiable and customizable (1)
•Modular and flexible (1)
(b) Video conferencing (1) and Internet phone (1)
(c) The written exercise can be submitted to the tutor through
•E-mails (1)
•Online forums (1)
•FTP servers (1)
•Learning portals (1)
(d) •Written examinations (1)
•Presentation in front of the audience (1)
2. (a) Completeness / accuracy / objectivity / timeliness / legality
(any four × 0.5)
(b) III > I > II
E-books from the library contain more reliable information from authors and
publishers. In discussion forums, the messages can be posted by anyone which can
be faked. (1)
(c) II > I > III
People can post messages on discussion forums almost instantly while e-books
from the public library need time to be processed, it may not be up-to-date. (1)
(d) (i) Taiwan train schedule (1)
(ii) Taipei sightseeing / Taipei tourist information (any one × 1)
(iii) Taiwan tourist information / Taiwan official tourist (any one × 1)
(e) (i) ‧Credit card payment through the Internet
‧Account transfer through e-banking
‧PayPal
(any two × 0.5)
(ii) ‧No time constraint (1)
‧Reduce the administrative costs (1)
(iii) ‧Fake web site (1)
‧Sensitive information may be stolen during the transaction. (1)
4 × 1,024 2 × 8
3. (a) The time taken to download the whole video file = seconds (2)
800 × 1000
= 41.9 seconds (1)
4 MB
(b) The file size played per second = (2)
20
= 0.2 MB
= 204.8 KB (1)
(c) Let t be the duration out of the 20 seconds of video which has not yet been
downloaded.
The data size which has not yet been downloaded = 204.8t KB (1)
204.8t KB
Time needed to download the remaining video file = (1)
800 Kbps
1638.4t × 1024b
=
800 × 1000bps
= 2.097t seconds (1)
Since the whole video lasts for 20 seconds, 2.097t must be less than or equal to 20
so that the video playing will not be interrupted.
Hence, 2.097t = 20 (1)
t = 9.537 seconds (1)
20 − 9.537
The percentage of video file downloaded = × 100% (1)
20
= 52.3% (1)
