This dissertation explores the relevance of computer science to physics. Beginning with a thorough technical analysis of the concept of information and theoretical computer science I distinguish between computation simpliciter and the narrower notion of digital computation which I define as symbol manipulation. I develop a detailed account of what it means to say a physical system implements, or carries out, a computation. I discuss the difference between analogue and digital computation and conclude it is a false dichotomy. A new category of device known as an experimental computer is proposed and distinguished from an analogue computer. I critique Geroch and Hartle's desideratum that all scientific theories be computable and I finish by looking at several attempts to define 'complexity' in computational terms.