Extern Storage Class

Extern Storage Class

• Identifiers declared in the global scope by default have extern storage class
• We can also access extern variables of one file to another file. But make sure both files are in same folder.
• extern variable cannot be initialized if a declaration statement is written within the block or local scope
• The extern storage class specifier cannot be used in the parameter declaration either in the function declaration or in the function definition

Example

#include<stdio.h>
#include<conio.h>
extern int a=200;
int main()
{
	printf("a = %d\n",a);
	return 0;
}

Output

C:\TDM-GCC-64>gcc extern.c -o extern
extern.c:3:12: warning: 'a' initialized and declared 'extern'
 extern int a=200;
         ^
C:\TDM-GCC-64>extern
a = 200

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