Can we use structure written in a header in another header without calling header

Hi All,
Can we use structure or function or variable written in a header into another header without including name of header of which we are going to use the struc or func or variable of that particular header

for ex:
file.h header has

Code:

---

struct database {  int id_number;  int age;  float salary; };

---

And i also have a header data.h
can i use the struct mentioned above into data.h without using
#include<file.h> in data.h file. I think we cannot but i am in situation where a header uses another header without #include defination.
could not understand why is that... Kindly help me out

Thanks n Regards.

What do you mean by "using a header without #include"? Normally if you try to use a struct database without including the file.h header your compiler should tell you that it does not know this structure.

There are times with the second header only needs to know that database is a structure; in that case adding this line in the second header will work. IIRC, this is called a forward declaration.

Code:

---

struct database;

---

Tim S.

Many Thanks ... !!! Will look into it...:)

Technically... if the source file you are compiling includes file.h before data.h then it should work although it is not something I would recommend. Doing things that way forces a requirement that header files be included in a certain order, this is to be avoided.

Thanks a ton..!! Its all clear now ... :) That is what happening in source file ... :)