=================================================================

              #ifdef                  #ifndef

The above preprocessor statements are used when you wish to
include/exclude code based on weather something was declared using
the #define preprocessor statement. The #ifdef will include the
code if the target IS defined. The #ifndef will include the code
if the target wasn't defined.

%^CYAN%^%^BOLD%^-----< Syntax for #ifdef statements >-----

#ifdef %^MAGENTA%^%^BOLD%^<target>

%^BLACK%^%^BOLD%^     <block of statements here>

#endif

The #ifdef checks to see if the <target> was defined with #define.
If it was defined, The block of statements are compiled into the
object. You may also use the #elseif and #else preprocessor
statements with #ifdef. Please see %^CYAN%^%^BOLD%^coding conditional_compiling%^RESET%^.

The syntax for #ifndef is the same as #ifdef. The differance other
than swapping #ifndef for #ifdef is that #ifndef will only include
the block of statements if the <target> was NOT defined.

=================================================================

Ironman

PS -- You can see samples of #ifdef and #ifndef at work inside
      most header files.

