The Java Virtual Machine is the software implementation of a CPU designed to run compiled Java code. Using the Java Virtual Machine (JVM) makes it possible to develop additional syntaxes for expressing the problems you want to solve and gives more control over the performance of your application. This text is a comprehensive programming guide for the Java Virtual Machine. Providing an overview and reference of the JVM, it enbles users to create their own implementations of the JVM or write their own compilers that create Java object code. The book is divided into two sections: the first includes information on the semantics and structure of the JVM; the second is a reference of the JVM instructions, or opcodes. The programming guide includes numerous examples written in Java assembly language. A Java assembler is provided with the book, so the examples can all be compiled and executed. The reference section offers a complete description of the instruction set of the VM, and the class file format including a description of the byte-code verifier.