The C standard formalized in Coq
I would strongly encourage anyone interested in formal methods (and formal proofs in particular) but may be intimidated by dependent types, which serve as the basis for Coq (and are foreign not only to software developers but to most mathematicians as well) to give TLA+[1] a look. It is a decade younger than Coq (16 vs. 26), but simpler to use, much more gradual, and has had industry adoption pretty much since its inception.Instead of dependent types (in fact, TLA+ is untyped[2]) It is based on simple ZF set theory and logic, and should be immediately familiar to anyone who's taken even one logic (or discrete math) course in college. In addition to a proof assistant it has a good model checker, comes bundled in a nice (relatively speaking) IDE, and is easy to learn (with a thorough tutorial written by Leslie Lamport himself).TLA+ is also more widely used in the industry -- both hardware and software -- perhaps most notably in the software industry by Amazon, who use TLA+ to specify many of their AWS services. TLA+ is a formal specification (and verification) tool designed for engineers and used by engineers. Although, to be fair, neither tool is used by a large portion of the industry.EDIT: Removed potentially incendiary Lamport quote.EDIT: Changed an incorrect statement about Coq's use in the industry[1]: http://research.microsoft.com/en-us/um/people/lamport/tla/tl...[2]: See Should Your Specification Language Be Typed? by Lamport and Paulson: http://research.microsoft.com/en-us/um/people/lamport/pubs/l...