What is the difference between Extern and global variables?

Answer 1

first of all understand external variable:

Ex:

file1.c
----------

#include stdio.h

extern int a;
int main()
{
printf("%d",a);
return 0;
}

file2.c
----------
int a=5;

whey ever we want to use a variable declared in one file into another file at that time we use extern keyword

in above example variable 'a' is declared in file1 (here memory is not allocated for that variable it's only declared) in file2 value is defined to that variable.(memory is allocated)

Global variable:

with in the one file anywhere we can use it.

Answer 2

extern variables are only declared where as global variables are declared and defined.Both are visible through out the program

Answer 3

🎃#H P 22™🎃 Okay, so global variable can't be accessed in another module, right?

Answer 4

Aditya rout So, by program, you mean all the modules

Answer 5

I'm still not clear. If global variables can be accessed in any module then what's the use of extern variable

Answer 6

Bhargava Ram Got it finally 😌, thanks 😇... and yes suppose we defined a global variable before main () in file 1.c then can we use it in file2. c?? and is it necessary to include the file which contains the definition of extern int a;

Answer 7

Okkayy

Answer 8

Ya was also having the same doubt

Answer 9

Sneh Chauhan suppose we defined a global variable before main () in file 1.c then can we use it in file2. c?? and is it necessary to include the file which contains the definition of extern int a;

Not mandatory to use second file
We can use extern variable in inside a file also,
We can define that extern variable value in file1.c also

file1.c
-----------
#..............
Extern int a;
int main()
{
printf("%d",a);
fun1();
fun2();
}

Void fun1()
{
printf("%d",a);
}
int a=5;
}

Void fun2()
{
printf("%d",a);
}

other difference is

declaration and value assign is not possible at a time in extern variable.

in global variable declaration and value assignment is possible at same time.

Answer 10

Yes,by program all modules.You have to declare extern variable before the main().

Answer 11

I can't get it clear