Class constructor syntax question

[Peyton]

Hi,

I had this constructor given to me.

// Screen's constructor
Screen::Screen(int_s height, int_s width, char bkground):
	_height(height),// initialises _height with height
	_width(width),  // initialises _width with width
	_cursor(TOP_LEFT),		// initialises _cursor to the starting position
	_screen(height * width, bkground)	// size of _screen is height * width
{ ...
some code 
... }

What's the : operator doing? And why not rather change the data members (_height,_width,_cursor) inside the {}?

Thanks :)

[hamsterman]

http://www.cprogramming.com/tutorial/initialization-lists-c++.html