I mean that it may return whether how many no of variables printed or how many bytes of variables to be printed.

printf function is library function and and you can also include own library function in c language using header file.
printf function does not return any value not even void.

printf function return the total number of characters (or can say bytes) to be printed on the screen.It doesn't return number of variables.
As a proof you can compile below progam and run it will return 9
#include<stdio.h>
void main()
{
int i=0,j=100,z;
z=printf("i=%d j=%d",i,j);
printf("%d",z);
}

Hello,

Printf() will return the number of arguments it prints

Hi
printf will return number of character passed to the fierst string......

print f ( ) returns the number of characters are passed within " " (double quoted).

I agree with Kailash, it returns the number of characters the function prints on the display device...