Critical Code contemplates Department of Defense (DoD) needs and priorities for software research and suggests a research agenda and related actions. Building on two prior books--Summary of a Workshop on Software Intensive Systems and Uncertainty at Scale and Preliminary Observations on DoD Software Research Needs and Priorities--the present volume assesses the nature of the national investment in software research and, in particular, considers ways to revitalize the knowledge base needed to design, produce, and employ software-intensive systems for tomorrow's defense needs. Critical Code discusses four sets of questions: * To what extent is software capability significant for the DoD? Is it becoming more or less significant and strategic in systems development? * Will the advances in software producibility needed by the DoD emerge unaided from industry at a pace sufficient to meet evolving defense requirements? * What are the opportunities for the DoD to make more effective use of emerging technology to improve software capability and software producibility? * In which technology areas should the DoD invest in research to advance defense software capability and producibility?