cerr is very similar to cout. It is used to output a message. But in this case it is used to display error messages.

Nice, we use the same header file!

This looks very similar to cout! The difference is you should always use cerr for errors and cout for regular output.

Whoopsie! I can see why you'd think that but if this is an output do you think we need a different header file to what we've already seen?