1 Introduction

The information in this document was collected through investigation of the R source code, mostly in the files src/include/Rconnections.h, src/main/connections.c, the files that reference the functions and symbols therein, and the Subversion commit log over the past ten years. The concepts presented in this document are current to R version 2.12.0 (R-devel, r52500). These notes are collected and released purely to satisfy the interests of the author, and hopefully other R enthusiasts.

The content of this document assumes familiarity with the C and R programming languages, and some familiarity with the infomation contained in the R Internals manual. Readers are encouraged to follow along with the R source code in the appropriate sections, which may be obtained from one of the CRAN mirrors.

For the past ten years, the R connections internals have been fairly stable. Most changes to the internals have related to the addition of new connection types, most recently the clipboard connection types, and changes to the character re-encoding mechanism. Currently, and over the past ten years, the primary contributor (committer) to the connections internals is Professor Brian Ripley of the University of Oxford, though several other members of the R core development team have also contributed.