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<META name=vsisbn content="1558515682"><META name=vstitle content="Java Digital Signal Processing"><META name=vsauthor content="Douglas A. Lyon"><META name=vsimprint content="M&T Books"><META name=vspublisher content="IDG Books Worldwide, Inc."><META name=vspubdate content="11/01/97"><META name=vscategory content="Web and Software Development: Programming, Scripting, and Markup Languages: Java"><TITLE>Java Digital Signal Processing:Java and Its Promise</TITLE>
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<H2><A NAME="Heading1"></A><FONT COLOR="#000077">Chapter 1<BR>Java and Its Promise
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<P>This chapter introduces Java’s good points, and its not so good points. Any overview of Java must discuss the language specification and the language programming environment. Collectively, these are called <I>Java technology</I> and can include hardware as well as software.</P>
<P>This chapter is divided into Five main sections.</P>
<P>The first section, “What Is Java and Where Did It Come From”, introduces the Java technology. We show that the term <I>Java</I> has come to mean both the Java programming language and the technology needed to support it.</P>
<P>The second section, “The Big Idea: WEBOS,” describes the state of the art. We give an overview of the picoJava technology, the core of the Java chips that Sun intends to release. We also describe what may happen when Java appliances become widely used.</P>
<P>In the third section, “Java: The Good, the Bad, and the Ugly,” we tell it like it is. Java has some good features, but it also has problems. This section outlines both. Please keep in mind that we really like Java (no, really). Still, we do not pull any punches. Every programming language has problems, and Java is no different. You should put your best foot forward, but watch where you are putting it.</P>
<P>The fourth section, “The HTML Model vs. the Java Model,” describes the HTML (Hypertext Markup Language) model that is the basis of the World Wide Web and discusses the current problems with the diverse nature of data representations. You will also find diccourse on the big idea behind the Java model and how it may help to reduce the decoding problems that our Web browsers currently face.</P>
<P>In the fifth section, “The Java Developer Environments,” we review a few software products—some of which are very useful. You’re advised to select a programming tool with care. Often this means budgeting for more than one compiler and testing it yourself.</P>
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<P><FONT SIZE="-1"><HR><B>CD-ROM: </B>The fifth section, “The Java Developer Environments,” summarizes how you can get started using the software that comes with this book.<HR></FONT>
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<H3><A NAME="Heading2"></A><FONT COLOR="#000077">What Is Java and Where Did It Come From?</FONT></H3>
<P>The term <I>Java</I> refers both to a language and to a technology that supports the language. When we speak of the <I>Java programming language</I>, we are talking about an object-oriented language developed by Sun Microsystems. Syntactically, this language is similar to several others. It has the braces of C, C++, and Objective C. It has the exception model of ZetaLisp, a flavors-based LISP that ran on LISP machines. The same method of exception handling has been proposed by Bjarne Stroustrup for use with the ANSI C++ standard [Spuler].</P>
<P>When we speak of <I>Java technology</I>, we are talking about the Java programming language and its support systems. These systems include a large library of classes called the <I>Java class libraries</I>. Java technology also includes a specification for run-time behavior, which is achieved using a Java machine specification. Java technology suggests that the Java machine may be implemented using any combination of software or hardware. When the Java machine is implemented in software, it is called the <I>Java virtual machine</I>.</P>
<P>Java started life as a language called Oak. It was designed to incorporate the best features of several languages into a single, new language. Just as important, features that were thought to make the language less reliable were left out. In balancing speed and reliability, Java’s designers chose reliability. This design criterion makes Java inherently different from, for example, C++. In C++, features have been added to the language, but none have been removed. Further, it was important that C++ run as fast as C [Stroustrup].</P>
<P>One of Java’s design objectives is that it be useful for distributed computing. In the distributed computing model, code can be downloaded for execution on demand in a secure fashion. Security became an important issue. If the code’s source was not trustworthy, the code had to be treated as potentially harmful to users’ data and computer hardware. Danger to users’ data could include access to and distribution of sensitive information, such as credit card numbers, bank account numbers, and other proprietary data.</P>
<P>The Java machine specification is a Java language support technology that has become an integral part of the language. The tight integration of the Java language with the Java machine specification is one of Java’s main selling points. The Java virtual machine places a layer of isolation between the running Java program and the underlying hardware, providing security and portability. The Java virtual machine provides security by optionally creating a security manager, that can keep a program from performing tasks that are considered a security risk. The Java virtual machine provides portability in that the virtual machine itself can run on several hardware platforms.</P><P><BR></P>
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