What is #if directive ?

The #if directive can be used to test the conditions or expressions. If the expression or conditions is true than it returns 0 (zero) other wise it return nonzero value and execution will go to next step or statement like as #else, #elif or #endif.

Syntax:

#if condition_1

                statement_1;

                ……………….

                statement_N;

#else

statement_1;

                ……………….

                statement_N;

#endif

Ex:

#if A > B

                #define MAX A

#else

                #define MAX B

#endif