Pair programming is an Extreme Programming practice, where two programmers working side by side on a single computer produce a software artifact. This technique has demonstrated to produce higher quality code in less time it would take an individual programmer. We present the COPPER system, a synchronous source code editor that allows two distributed software engineers to write a program using pair programming. COPPER implements characteristics of groupware systems such as communication mechanisms, collaboration awareness, concurrency control, and a radar view of the documents, among others. It also incorporates a document presence module, which extends the functionality of instant messaging systems to allow users to register documents from a Web server and interact with them in a similar fashion as they do with a colleague. We report results from a preliminary evaluation of COPPER which provide evidence that the system could successfully support distributed pair programming.