for what is the DDE server?

[MoonKid]

for what is the DDE server?

[killerbot]

it allows for the following functionality :

Say file types .xyz are linked to Program ABC

0) say ABC is not running
1) double click in explorer on a .xyz file --> ABC opens and shows/handles that .xyz file
2) double click in explorer on another .xyz file , if no DDE server (or a special wrapper exe), another ABC instance opens and shows/handles the second .xyz file; NOW in case of a DDE server (the program ABC runs that DDE server) the second .xyz file is opened by the first and only instance of ABC

This is probably something like 80% correct ;-) , but simple put, it's something like that.