ob[]={ {1,7},{15,25},{35,45},{55,65}};
point *a;
a=ob; // now a will contain the adress of ob[0].
a++; // now a will contain the adress of ob[1].
a->x++; // now ob[1]->x is incrimented ie.15 becomes 16
a++; // now a will contain the adress of ob[2]. ----------(1)
a->y++; // now ob[2]->y is incrimented ie.45 becomes 46
cout<<ob->x<<" "<<a-y<<endl;//ob contains adress of ob[0] so ob->x is 1
and a->y is 46 from (1)
cout<<ob->y<<" "<<a->y<<endl; //now ob->y is 7 and a->y is 46 from (1)
so it is
1 46
7 46
I hope it's clear If not ask;