Preface

Virtual Machine Specification, Java Card Platform, v2.2.2

Java Card

technology combines a subset of the Java trademark

programming language with a runtime environment optimized for smart cards and similar small-memory embedded devices. The goal of Java Card technology is to bring many of the benefits of Java software programming to the resource-constrained world of devices such as smart cards.

The Java Card platform is defined by three specifications: this Virtual Machine Specification for the Java Card Platform, Version 2.2.2, the Application Programming Interface for the Java Card Platform, Version 2.2.2, and the Runtime Environment Specification for the Java Card Platform, Version 2.2.2.

This specification describes the required behavior of the virtual machine (VM) for the Java Card platform ("Java Card virtual machine" or "Java Card VM"), version 2.2.2, that developers should adhere to when creating an implementation. An implementation within the context of this document refers to a licensee's implementation of the Java Card virtual machine, Application Programming Interface (API), Converter, or other component, based on the Java Card technology specifications. A "reference implementation" is an implementation produced by Sun Microsystems, Inc. Application software written for the Java Card platform is referred to as a Java Card technology-based applet ("Java Card applet" or "card applet").

Who Should Use This Specification

This document is for licensees of the Java Card technology to assist them in creating an implementation, developing a specification to extend the Java Card technology specifications, or in creating an extension to the runtime environment for the Java Card platform ("Java Card Runtime Environment" or "Java Card RE"). This document is also intended for Java Card applet developers who want a more detailed understanding of the Java Card technology specifications.

Before You Read This Specification

Before reading this document, you should be familiar with the Java programming language, the Java Card technology specifications, and smart card technology. A good resource for becoming familiar with Java technology and Java Card technology is the Sun Microsystems, Inc. web site, located at

How This Book Is Organized

Chapter 1, "Introduction" provides an overview of the Java Card virtual machine architecture.

Chapter 2, "A Subset of the Java Virtual Machine" describes the subset of the Java programming language and Java Virtual Machine ^[1] that is supported by the Java Card specification.

Chapter 3, "Structure of the Java Card Virtual Machine" describes the differences between the Java virtual machine and the Java Card virtual machine.

Chapter 4, "Binary Representation" provides information about how programs written for the Java Card platform are represented in binary form.

Chapter 5, "The Export File Format" describes the export file used to link code against another package.

Chapter 7, "Java Card Virtual Machine Instruction Set" describes the bytecodes (opcodes) that comprise the Java Card virtual machine instruction set.

Chapter 8, "Tables of Instructions" summarizes the Java Card virtual machine instructions in two different tables: one sorted by Opcode Value and the other sorted by Mnemonic.

Prerequisites

This specification is not intended to stand on its own; rather it relies heavily on existing documentation of the Java platform. In particular, two books are required for the reader to understand the material presented here.

The Java Language Specification by James Gosling, Bill Joy, and Guy L. Steele (Addison-Wesley, 1996) ISBN 0-201-31008-2, contains the definitive definition of the Java programming language. The Java Card platform, version 2.2.2, language subset defined here is based on the language specified in this book.

The Java Virtual Machine Specification (Second Edition) by Tim Lindholm and Frank Yellin. (Addison-Wesley, 1999) ISBN 0-201-43294-3, defines the standard operation of the Java virtual machine. The Java Card virtual machine presented here is based on the definition specified in this book.

Related Documents

References to various documents or products are made in this manual. You should have the following documents available:

Typographic Conventions

TABLE P-1 Typographic Conventions
Typeface	Meaning	Examples
`AaBbCc123`	The names of commands, files, and directories; on-screen computer output	Edit your `.login` file. Use `ls -a` to list all files. `% You have mail`.
`AaBbCc123`	What you type, when contrasted with on-screen computer output Procedural steps	`%` `su` `Password:` 1. Run `cref` in a new window.
AaBbCc123	Book titles, new words or terms, words to be emphasized Command-line variable; replace with a real name or value	Read Chapter 6 in the User's Guide. These are called class options. You must be superuser to do this. To delete a file, type `rm` filename.

Acknowledgements

Java Card technology is based on Java technology. This specification could not exist without all the hard work that went into the development of the Java platform specifications. In particular, this specification is based significantly on Java Virtual Machine Specification. In order to maintain consistency with that specification, as well as to make differences easier to notice, we have, where possible, used the words, the style, and even the visual design of that book. Many thanks to Tim Lindholm and Frank Yellin for providing a solid foundation for our work.

Accessing Sun Documentation Online

The Java Developer Connection trademark

program web site enables you to access Java platform technical documentation on the web at

Sun Welcomes Your Comments

We are interested in improving our documentation and welcome your comments and suggestions. You can email your comments to us at docs@java.sun.com.

^{1 (Footnote) The terms
"Java Virtual Machine" and "JVM" mean a Virtual Machine for the Java
platform.}