How is "highscorer" undefined in this code?

programming flash
1

I can’t figure this out yet I’m new to actionscripting… so this should be easy for any veteran…

if (_global.score > _global.highscorer){
_global.highscorer == _global.score;
}

Thanx

And another quick question:

Do all variables start out at the number 0 in actionscript…? I’m a C++ programmer and not used to actionscript yet.

Thanks for the help…again