#line directive in c

It tells the 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.

Example:

#include<stdio.h>

#line 15

int main(){

    int a=10;

    a++;

    a++;

    #line 5

    printf("%d",a);

}

If we will see its intermediate file then before the actual compilation the source code is expanded as :

In the very long c program for debugging purpose if we want to check the program after the line 300 by F7 key then we will write #line 20

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