Thread: headrs

hi all

Code:

#ifndef _HEADER_FILE_H
#define _HEADER_FILE_H
extern int x;
#endif

Code:

header_file.c
include "header_file.c"
int x;

main.c

Code:

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

int main()
{
     x=55;
         printf("&#37;d\n",x);
return 0;
}

now what is the question ?
the question in the variable x ;
it's declared in the header_file
the defined in the header_file.c
then used in the main.c
but what if i redefined it in main.c also like that
main.c

Code:

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

int main()
{
     int x=55;
         printf("%d\n",x);
return 0;
}

i tried and it work
so my question is ?
what has happen to the variable x in the header_file.c when i redefined the variable x in main .c again ?
and
i cannot allocate space like that

Code:

/*header*/
#ifndef _SS_H
#define _SS_H
extern int comp;
extern  char* all;
#endif

Code:

/*header source*/
#include "ss.h"
#include<stdlib.h>

int comp=14;
char *all=malloc(100*sizeof(*all));

error :ss.c:5: error: initializer element is not constant

so my question is why i cannot allocate space like that?
thanks

Variables local to whatever block you're dealing with, take precedence over variables declared in previous blocks. The basic concept of this is involved with what is called "scope".