What is use of #line directive?

by using #line directive compiler that next line of source code is at the line number which has been specified by constant in #line directive i.e it transfer the program control to the line number which has been specified by #line directive.

Ex :

#line 15
void main()
{
int a=10;
a++;
clrscr();
a++;
#line 5
printf(“%d”,a);
getch();
}