The Internet helped catapult Java to the forefront of programming, and Java, in turn,
has had a profound effect on the Internet. The reason for this is quite simple: Java
expands the universe of objects that can move about freely in cyberspace. In a network,
two very broad categories of objects are transmitted between the server and your
personal computer: passive information and dynamic, active programs. For example,
when you read your e-mail, you are viewing passive data. Even when you download a
program, the program’s code is still only passive data until you execute it. However, a
second type of object can be transmitted to your computer: a dynamic, self-executing
program. Such a program is an active agent on the client computer, yet is initiated by
the server. For example, a program might be provided by the server to display properly
the data that the server is sending.
As desirable as dynamic, networked programs are, they also present serious
problems in the areas of security and portability. Prior to Java, cyberspace was
effectively closed to half the entities that now live there. As you will see, Java addresses
those concerns and, by doing so, has opened the door to an exciting new form of
program: the applet.
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