What's the meaning of #line in C language?

Question

What\'s the meaning of #line in the C language? Where would it be used?

Answer 1

It is called the preprocessor line control directive.

The expansions of both __FILE__ and __LINE__ are altered if a #line directive is used. It causes the compiler to view the line number of the next source line as the specified number.

Its main use is to make the compiler provide more meaningful error messages.

You can find more explanation and a usage example in IBM's documentation.