Errors in code for software lead to failures both routine and catastrophic -- and to the vulnerabilities at the root of the escalating security crisis. Errors in code for people -- the human genome -- give rise to chronic conditions, devastating rare diseases and, for half of us, cancer. This talk addresses how to end errors in code -- both digital and biological -- through conservatively approximating solutions to the halting problem for the former and through a computational rethink of the practice of molecular or "precision" medicine for the latter. To evade the halting problem, I will present a broad, universal framework for conservatively approximating the behavior of programs and discuss the success of applying this approach to detecting and eliminating security issues in software. I will then provide a programmer's introduction and overview of precision medicine; argue that computation has becoming the limiting reagent in saving lives; and explain how a computational re-visioning to the practice of medicine is the key to the diagnosis, discovery and treatment of both rare genetic disorders and cancers.