DW vs CW differences

I have joined the CWOP back in September 2010. My call sign is DW4088. One thing I have always wanted to know is the differences between DWxxxx and CWxxxx prefixed stations. Like how do they decode call signs and designate them? What determinds that?

DW are continous as all CW where assign there is an note to that fact on the website.

basicly they ran out of CW numbers…and so DW numbers start over at 0000