In this chapter, we introduce high-performance computing. Broadly, computing may be slow because we have larger datasets and/or because we are doing more computations. We will talk a little about ways to deal with both in R. When people say high-performance computing or big data they can mean very different things. In this chapter we will not discuss processing terabytes of data or analyses that require large clusters. Instead, we only assume a fairly standard desktop or laptop that has at least two cores. Note that some of the code examples in this chapter may take some time to run. That is deliberate so it is both more realistic and starts to convey the "feel" of larger data. Making a typo can be more painful when it takes minutes or hours to get your result and you find out it is wrong and you have to run it again!