Why we are use the "#" in starting of any header file?????

Question

Gimme answers

Answer 1

It is the prefix to a preprocessor directive to do the following (after the #) before compilation.

Answer 2

It is a pre fix to pre processor directive (which process the source code before compilation).it tells the compiler that whatever the header file we are including using include directive process it because the all the functions we are gone to use will be from that header file

Answer 3

It is used to distinguish lines which need preprocessing before actual compilation begins. it replaces that line with all the text inside 'stdio.h'. it replaces all instances of ADD with definition of ADD. So # is used by Ccompiler to know which lines need preprocessing.