CODEWITHSUNDEEP
cfunctionvariablesscope
user6385115
user6385115

Reputation:

Functions and variables scope in C

Why we don't use extern when using function from one .c file in another .c file , but we must do extern for variables case? Is it related to linker?

Upvotes: 2

Views: 3886

Answers (5)

Ravi C
Ravi C

Reputation: 64

Yes, Let consider you have one .c file as process.c and you declared it in process.h . Now if you want to use the function from process.c to suppose tools.c then simply #include "process.h" in tools.c and use ther function. The process.h and process.c file should be in your project.

process.c file

#include<stdio.h>
#include<conio.h>
#include "process.h"
unsigned int function_addition(unsigned int a, unsigned int b)
{
 unsigned int c = 0;
 c = a + b;
 return c;
}

process.h:

<bla bla bla >
unsigned int function_addition(unsigned int a, unsigned int b);
<bla bla bla >

tools.c file:

#include<stdio.h>
#include<conio.h>
#include "process.h"
my_tools()
{
 unsigned int X = 1, Y = 9, C = 0;
 C = function_addition(X,Y);
}

All these files are in one project.

Upvotes: 0

msc
msc

Reputation: 34678

Demo program,

one.c

#include "one.h"

void func1() //defination
{
    //code
}

one.h

void func1(); //declaration

main.c

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

int main()
{
    func1();
}

Then compile program in Gcc Linux : gcc main.c one.c

Upvotes: 0

Fly
Fly

Reputation: 1

you can create a .hfile,declare functions you want to use in the other .c files and #include the .hfile in the other .c files.

Upvotes: 0

Quentin
Quentin

Reputation: 63154

Actually, function names act just like variable names, but function prototypes are extern by default.

From cpprerefence:

If a function declaration appears outside of any function, the identifier it introduces has file scope and external linkage, unless static is used or an earlier static declaration is visible.

Upvotes: 1

P.P
P.P

Reputation: 121427

Functions are extern qualified by default (unless you change it to internal with static). For example,

int func(void) {
}

extern int func2(void) {
}

Both func and func2 are external. The extern keyword is optional for external functions.

Upvotes: 3

Related Questions