Page 234 - DCAP404 _Object Oriented Programming

Unit 10: Virtual Functions and Polymorphism

Self Assessment Notes

Fill in the blanks:
13. A class that declares or inherits a virtual function is called a ………………………………..
class.

14. Polymorphism plays an important role in allowing …………………….. having different
internal structures to share the same external interface.
15. An essential feature of polymorphism is the ability to refer to objects without any regard
to their…………………. .



Caselet Betting on the Internet, PPP AIMS High

etting on the Internet to level the playing field, a small Chennai-based firm is
setting its sights high. The company, Plans Proposals & Projects (PPP), run by three
Bbrothers (who also constitute its entire staff), is looking to appoint distributors
worldwide for a software product it has developed using the Java programming language.
The software, PPPshar, enables several PC users to simultaneously access the Internet
using a single dial-up connection.
According to Mr. Parameshwar Babu, the product’s chief developer and the technical
expert in the trio, PPPshar could be used to hook up all the PCs (running Windows 95 and
a standard Web browser software) in a corporate network to the Internet using a single-
modem and a single phone connection. The software, priced at ` 5,000 per terminal (on the
user network), needs to be loaded only on the machine connected to the modem. It can
also be customised based on the user’s specific requirements.

PPPshar can be used with a dial-up TCP/IP Internet connection and there is no need for a
permanent Internet Protocol (IP) address as in the case of leased line connections. Provided
the product performs as claimed, the savings derivable from the software are quite obvious
for any organisation which wants to provide multiple Net connections to its members:
VSNL, currently the sole Internet Service Provider (ISP) in India, charges about ` 10 lakhs
annually for a high speed (64 kbps kilo bits per second) leased line connection compared
to ` 15,000 for a dial-up TCP/IP account (offering a maximum speed of 28.8 kbps).

Mr. Babu says that PPPshar would ensure that the speeds of the individual terminals in the
network do not suffer when multiple users are logged on to the Net. According to him, the
software keeps track of the “idle time” commonly encountered while surfing the Web
(that is, while locating and loading Web pages) and divides this time among the different
terminals.
“In any case, the individual speeds available to seven terminals simultaneously connected
through a 28.8 kbps modem compares favourably with 16 users splitting up a 64 kbps
leased line between them,” he says.
According to Mr. Babu, PPPshar can also be used by system managers to selectively
control access to certain types of information on the Net. For example, for a Chennai-
based medical college-cum-hospital, PPP has customised the software to ensure that Web
sites relevant to medicine can be accessed by the individual users.

Contd...

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