1You might expand the question by asking what ALGORITHMS are used to build bitcoin. – Tom Au – 2014-05-21T17:38:24.647

6@TomAu: That's a completely unrelated question. – Meni Rosenfeld – 2014-05-21T21:07:17.420

@MeniRosenfeld: Aren't the choice of programming languages tied at least in part to the kinds of algorithms you use? – Tom Au – 2014-05-21T21:31:26.793

2@TomAu: Not in the least. Most algorithms in use by Bitcoin are so commonplace that they've been ported to nearly every possible programming language. SHA256, ECDSA et al are all available in Bitcoin's native C++ as well as nearly any language you could name. This is a big part of why the various ports of Bitcoin's codebase sprung up so quickly: BitcoinJ (Java) already had the exact same building blocks to work with as Bitcoin Core (C++). – David Perry – 2014-05-21T22:17:46.210

4Asking 'what programming languages are used to build bitcoin' is like asking 'what programming languages are used to build TCP/IP'. Bitcoin, like TCP/IP, is a protocol - it is defined in a programming language neutral way, and can be implemented in any programming language. That said, you're most likely to find implementations in C++ and Java, but there's no reason why you couldn't write Bitcoin software in Python or anything you want. – Patashu – 2014-05-22T00:53:54.073

@Patashu: That's what I didn't understand. Thanks for clearing things up. – Tom Au – 2014-05-22T01:06:31.790

The question should be: What libraries exists for various Programming Languages to build bitcoin applications? – Stefan – 2016-02-01T07:17:57.137