The **`#line` directive** is one of the widely used directives in C. Its main purpose is to reset the line number and `filename` in the code. This means that we can reset any line of code to an arbitrary line number or a `filename` defined by the user. 


# Syntax
```
#line <new line number> <new file name>
```
# Code
Let's look at a code example for the use of `#line`. 


#include <stdio.h>	

int main()
{	
	
	printf("Hello world\n"); // this is line 6
	printf("Line: %d\n",__LINE__);	// printing line number, line 7

	#line 23	//reseting to 23, although next line number is line 10. 
	printf("Line: %d\n",__LINE__);	// printing line number
	printf("Line: %d\n",__LINE__);	
	printf("Line: %d\n",__LINE__);

	// let's try with filename (main.c) as well. 
	
	printf( "Line: %d, File: %s\n", __LINE__, __FILE__ );
	// now we use line to reset filename to "new_filename.c"
	// line number is set to 83
	#line 83 "new_filename.c"
	printf( "Line: %d, File: %s\n", __LINE__, __FILE__ );
	
	return 0;
}

What is the #line directive in C?

#line resets the line number and filename in C code, allowing custom line numbers or filenames.