Software plays a central role in all aspects of reversible computing systems, and a variety of reversible programming languages have been developed. This presentation highlights the principles and main ideas of reversible computing viewed from a programming language perspective with a focus on clean reversible languages. They are the building material for software that can reap the benefits of reversible hardware and interesting in their own right.

Reversible computing is situated within programming languages in general, and the relevant concepts are elaborated, including computability, injectivization and reversibilization. Features representative for many reversible languages are presented, such as reversible updates, reversible iterations, and access to a program's inverse semantics. Metaprogramming methods of particular importance to reversible programming, are introduced, including program inversion and inverse interpretation. Our presentation is independent of a particular language, although primarily the reversible language, Janus, will be used in examples.