#include <> vs #include ""

[girishpadia]

Hello Everyone,

I am new to Qt programing. I have seen following two different syntax to include files.

#include <Class>


and

#include "HeaderFile.h"

I could not get the fundamental difference between this two syntax. I understand that the first one include the class and second one includes the header file. But I am unable to understand which syntax to use in different circumstances.Which syntax consumes more memory ?

Many thanks in advance.

[symbianyucca]

here's one answer: http://www.geekpedia.com/KB113_What-...otandquot.html

Basically you would use "" for local includes

[girishpadia]

Thanks symbianyucca,

The link explains the difference for C++. How Qt interpretes both ? Because I have seen following syntax in Qt Examples.

#ifdef Q_OS_SYMBIAN
#include "qsysteminfo.h"
#else
#include <QSysInfo>
#endif

Does it depend on the target device to compile ?

[symbianyucca]

QT is C++ in the end, so would consider it to work same way. Though your example, appears to say that Symbian version would not make any difference on them. Anyway for future compatibility, it would be better to stick on doing it as it should be done..

[danhicksbyron]

"<>" is used for the standard header files -- searches a "wired in" list of headers -- while "" searches both the standard header file list and the list of header files supplied by the complier user (or the toolkit). In general one can use "" instead of <>, so long as the header file being referenced isn't duplicated in the user-supplied list (which is generally a bad idea anyway). Using <> instead of "" is less likely to work, however.

(The whole thing is really a little bit silly, and if it were done all over again it's likely that a different scheme would be used -- either no distinction at all or a finer-grained distinction.)

Note that this has nothing to do with whether the header file ends in ".h" or not -- if you look at the "QSysInfo" (no ".h") header file, for instance, it's just a #include for another header file (this one with ".h").