Along with the increasingly important runtime engines pervasive in our daily-life computing, there is a strong demand from the software community for a solid presentation on the design and implementation of modern virtual machines, including the Java virtual machine, JavaScript engine and Android execution engine. The community expects to see not only formal algorithm description, but also pragmatic code snippets; to understand not only research topics, but also engineering solutions. This book meets these demands by providing a unique description that combines high level design with low level implementations and academic advanced topics with commercial solutions. This book takes a holistic approach to the design of VM architecture, with contents organized into a consistent framework, introducing topics and algorithms in an easily understood step by step process. It focuses on the critical aspects of VM design, which are often overlooked in other works, such as runtime helpers, stack unwinding and native interface. The algorithms are fully illustrated in figures and implemented in easy to digest code snippets, making the abstract concepts tangible and programmable for system software developers.