what are the meanning of the two directives?

[shenh]

I download GAlib source codes for my optimization problem. But i cannot understand the meaning of two lines of codes in ga.h.

#ifndef _ga_ga_h_
#define _ga_ga_h_

I am not sure which OS is it applied. What is the difference between
#ifndef GA_H
#define GA_H

Thanks for any advice. If someone has just worked on GAlib, i am having some other trouble with it, and will appreaciate if you can lend me a hand.

Hailiang

[Bazzy]

http://www.cplusplus.com/forum/articles/10627/#msg49679

There's no much difference between

#ifndef _ga_ga_h_
#define _ga_ga_h_ 

and

#ifndef GA_H
#define GA_H 

They are both header guards -see link-

[shenh]

Thanks Bazzy for your quick response. I get it. It does not matter what you put after #ifndef, it just let the proprocessor know it has been included.

Hailiang