Hi I have a program, say file1.c which included file1.h, the header file which had lots of #define macros and structure definitions used by file1.c

I have decided to split the source code into 3 separate files (for logical reasons)

file1.c
file2.c
file3.c

Each of these have a corresponding header file which contain only function prototypes:

file1.h (I renamed the earlier file1.h, which had all the #defines and structure defs. to, say, abc.h)
file2.h
file3.h

So, Earlier everything was in file1.c. I removed a set of related functions and put them in file2.c, And another set of related functions and put them in file3.c


file1.c includes...

Code:

#include "file2.h"
#include "file3.h"
#include "abc.h"

file2.c includes..

Code:

#include "file1.h"
#include "abc.h"

file3.c includes..

Code:

#include "file1.h"
#include "abc.h"

Now my question is:

1) What would be an appropriate name for abc.h ?? This has lots of #define macros and structure definitions which is used by all three source files (file1.c, file2.c and file3.c) and hence is #included by all 3 of them.

2) Suppose the original source code had LOTS of global variables. The variables are used by all 3 source files. So how do I deal with them ? Can I put all these global variables in a header file and include it in all the 3 source files ? Will that work ? Or should I leave the global variables in file1.c and then declare them as "extern" in file2.c and file3.c ? (keeping in mind that there are LOTS of them).

3) Can header files contain variable declarations/definitions ???

What happens if I have a header file which has:

int a = 5

and I include this file in a some .c file and use 'a' and change its value ?

Thanks in advance..