Thread: C header files?

hi,

I ve questions bout header files...
for example if I have main function like below, how can i separate it into .c and .h files, to make it neat and more efficient..

Code:

#include <stdio.h>

#define  ASIZE        5000

int number = 0; /* Global int declaration */

struct data
{
	int  key;
	char *word;
} Data;

	/* Functions Prototype */

void function1();
int function2 ();
void function3();

              /* Main Program */

int main( void )
{
      // main program here......
     // and here here here....etc etc

      return 0;

}

              /* Functions */

void function1()
{

    return;
}

int function2()
{
    .....
}

void function3()
{

}

is that posibble to separate all the functions and the main program (into separate .c files)?? if yes, how can i link both of them when compiling?

thanks in advance,

CyC|OpS

hi David,

thanks for your explanation...very clear

now how to compile it?
issit only calling the main.c

eg: gcc main.c

or i need to call the dependecies too? .h and functions.c?

thanks...

CyC|OpS

so in this case, inside maindriver.c
in the main function
can I still use the functions from function.c? when I have only included function.h?
eg

#include<stdio.h>
#include "function.h"

int main (void)
{
void function1();
return;
}


Oh, btw, how do you type in codes in this forum properly?
like you guys have
code:
------------------
the codes
------------------

>now how to compile it?

A useful method is using make-files. See a guide to using makefiles here:
http://www.delorie.com/djgpp/doc/ug/...makefiles.html

>can I still use the functions from function.c? when I have only
>included function.h?

Yes, but you can use the function only if function.c is linked with maindriver.c.

>Oh, btw, how do you type in codes in this forum properly?

It's like this, but then without the spaces between it:

[ code ]
/* Code */
[ / code ]

Code:

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

/* function here...*/

#endif

how is this #ifndef & #endif work??
do i need to call FUNCTION_H inside the maindriver.c? or inside function.h? coz i didnt see any connection between maindriver.c or funtion.h with functions.c

thanks,

Ferdinand

These are preprocessor directives. It prevents from including the header-file more then once.

In normal language your code is as follows:
If FUNCTIONS_H is not defined, then define FUNCTIONS_H. Include the code until #endif is reached. The second time the file is passed, FUNCTIONS_H is already defined, so FUNCTIONS_H does not need to be defined anymore and the code will not be included.

>do i need to call FUNCTION_H inside the maindriver.c?

FUNCTIONS_H is a defined symbol, it is not a function which you can call.

####

Example:

I have a file called test.c in which a function test() is defined which displays a text on screen. The file is as follows:

Code:

/*TEST.C*/
#include <stdio.h>
#include "test.h"

void test ()
{
    printf ("This is a test\n");
}

The header-file contains the prototype of test().

Code:

/*TEST.H*/
#ifndef TEST_H
#define TEST_H

void test ();

#endif

This all is used by the main() function.

Code:

/*MAIN_TEST.C*/
#include "test.h"

int main (void)
{
    test ();
    
    return 0;
}

Hope this explains a little.

anyone can help? I ve worked on it for the whole night and still can't figure it out...

*_*

there's no error when i compile the object files
> gcc -c maindriver.c
> gcc -c functions.c

however it gives errors when
> gcc -g -Wall -o progname maindriver.o functions.o

the prog working before separated into functions.c and functions.h...

exactly!!!

I ve one variable which i declared as global variable inside header file..and i didnt declared it in other source file...

int var = 2;

how can i overcome this prob??

CyC|OpS