I like to think of exchanges as an unacknowledged patch to the Bitcoin protocol as it stands in 2019. Or even as it stood in 2012 or 2011. No, they're not in

I like to think of exchanges as an unacknowledged patch to the Bitcoin protocol as it stands in 2019. Or even as it stood in 2012 or 2011. No, they're not in the source code itself, but without them the project would still be sputtering along in almost total obscurity, if not abandoned altogether by now.