Identical line of code working in a single visible studio challenge, however not in one other – C++

Hey,
I got here throughout this very unusual drawback. I’ve 2 visutal studio challenge, and in each of them I’ve within the header file this:

class GameScene: public cocos2d::Scene{
//...some code
personal:
    boolean KEYS[255] = {false};
}

In one of many challenge every thing workd completely, no errors. Within the different one, actually the very same line errors with this:

I’ve absolutly no concept what’s going on. And being new to cpp, I’m having bother understanding the errors. What is admittedly puzzling is that it solely fails in a single challenge. ¿¿??

thanks

okey, I solved it…sort of.
As an alternative of “boolean”, I used “bool” within the second challenge and it labored. However why does “boolean” work within the different challenge?