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Fig. 1.16 | Drawing a yellow oval on the mouth to make a smile.
9. Exiting the Painter application . To exit the Painter application, click the Close
button (in the window's upper-right corner on Windows and the upper-left cor-
ner on Linux and OS X). Closing the window causes the Painter application to
terminate.
1.11 Internet and World Wide Web
In the late 1960s, ARPA—the Advanced Research Projects Agency of the United States De-
partment of Defense—rolled out plans for networking the main computer systems of ap-
proximately a dozen ARPA-funded universities and research institutions. The computers
were to be connected with communications lines operating at speeds on the order of 50,000
bits per second, a stunning rate at a time when most people (of the few who even had net-
working access) were connecting over telephone lines to computers at a rate of 110 bits per
second. Academic research was about to take a giant leap forward. ARPA proceeded to im-
plement what quickly became known as the ARPANET, the precursor to today's Internet .
Today's fastest Internet speeds are on the order of billions of bits per second with trillion-
bit-per-second speeds on the horizon!
Things worked out differently from the original plan. Although the ARPANET
enabled researchers to network their computers, its main benefit proved to be the capa-
bility for quick and easy communication via what came to be known as electronic mail (e-
mail). This is true even on today's Internet, with e-mail, instant messaging, file transfer
and social media such as Facebook and Twitter enabling billions of people worldwide to
communicate quickly and easily.
The protocol (set of rules) for communicating over the ARPANET became known as
the Transmission Control Protocol (TCP) . TCP ensured that messages, consisting of
sequentially numbered pieces called packets , were properly routed from sender to receiver,
arrived intact and were assembled in the correct order.
 
 
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