is part of the C text preprocessor: it does a text replace of the first part with the second part. You can do more with it than that, but that's the general idea - all it ever does is replace text: C Language: #define Directive (macro definition)
So everywhere in your code you write
in your code it will be replaced with
"%s me "
is there to make code more readable:
#define true (1==1)
#define false (1==0)
#define strDbConnect "Server=[SqlDev];Database=[Accounts];password=[NONE];user = [ME]"
So you can write stuff like this:
And make it easy to read (and safer, because the DB string is only entered once in the whole program).
I agree with KarstenK - the code you show is just stupid nonsense.