This chapter examines that aspect of the R process, with emphasis on how extensions to R should work with the process. The computations are best understood in terms of the three fundamental principles. The chapter describes how the three principles translate into the key components of the R process: the objects, the functional computations and the basic interfaces. The R evaluator uses the components to carry out users' computational requests. Dynamic languages such as R create similar data structures in response to computations. Function calls or the equivalent have been central to nearly all programming languages. For programming in a package, computations will take place in a function, assigned in the namespace of that package. The package implementation will control what objects from other packages are in the enclosing environment of the namespace. The parent of that environment is composed of the objects imported into the package, and the parent of the imports environment is the base package.