A demonstrably correct compiler

As critical applications grow in size and complexity, high level languages, rather than better-trusted assembly languages, will be used in their development. This adds potential for extra errors to creep in, especially in the now necessary compiler. To avoid these new errors, it is necessary to have a formal specification of the high level language, and a formal development of its compiler. We outline what we believe is a practical route for achieving a demonstrably correct compiler, and describe a prototype compiler we have built by this route for a small, but non-trivial, language.