What Is the Oldest Code Written Still Running?

Consul writes "What is the oldest piece of code that is still in use today, that has not actually been retyped or reimplemented in some way? By 'piece of code,' I'm of course referring to a complete algorithm, and not just a single line." The question would have a different answer if emulation, in multiple layers, is allowed.

Comments

Please don't use anecdotal evidence.

[suso]

You are not presenting any real evidence that it is the case. You are just saying this because it sounds likely to be true, but do you have any hard evidence to back it up?

Unfortunately, it looks like people aren't going to take this question seriously.