pointer,macros

[guna8985]

someone pls help me understand macros

#ifdef
#endif

#ifndef
#endif

also about '->' operator.

and pointers.those probs eating my brain. int *a; and int* a; is it same ?

what if it has double star. int **a; int** a;


Pls reply me with a image processing example which includes answers to my questions.

[hamsterman]

http://www.cplusplus.com/doc/tutorial/preprocessor/##ifdef

ptr -> something is equivalent to (*ptr).something

int *a is the same as int* a

int** a is a pointer to a pointer to an integer.

Pls reply me with a image processing example which includes answers to my questions.

what?