About confusion of lesson for c++

Hi,I am learning this lesson:

I don’t understand why should we search : “C%20%20 undefined reference to main” instead of simply the undefined reference to main. What does C %20 %20 mean here?

It could possibly be a typo related to url-encoding (%20 is a space character).

The better google search is C++ undefined reference to main.

In a meta sort of way, it kind of is the mood of debugging in C++. Error messages in C++ can be cryptic and sometimes you have to deduce not what they are, but what they mean to be. It takes a long time to get used to them.