void (*P[4])() = {A,B,C,D};
P is an array of pointers to functions and the size of the array is 4. The array is initialized to point to the functions A, B, C, D.
P |
Pointer to A |
P+1 |
Pointer to B |
P+2 |
Pointer to C |
P+3 |
Pointer to D |
In the for() loop each function is called.
So, the output is ABCD.