How are discs burned?

[dbminter]

When data is written to a disc, is it from the inner edge to the outer or outer to inner?  I'd have to say it's inner to outer as when you don't burn a full disc, the inner edge is full but data is not written to the entire outer edge.  And, is it the same for all media?  CD, DVD, and BD?  I'd also have to say yes for the same reason I just said.  CD's have full inner edges but data not written to the outer edge.  Same with DVD and BD.  Thanks!

[LIGHTNING UK!]

Everything's inner to outer.