Why, of course. What's more interesting, I can find only one GUI app on my computer that is (probably) written in C++, the web browser I use.

Why do you ask?

His argument is that if he's using a Mac, a lot of them are written in Objective-C.

And if he's using Gnome in Linux, most are written in C.

But for Windows apps, commercial apps, cross platform and games, C++ leads by far.