static modifier function in C language

The static modifier function means that the function is visible only inside the module.

Because in C, the function is external. The function, no matter what file it is written in, is visible in other files.
To restrict a function from being visible only in one source file, you can use the static indicator.

Do not want C + + language, before using a function, you must have the signature of the function, C and need.

Test code:

////////////////////////////////////////////
test1.c
int fun ()
{
return 1;
}

int static fun_static ()
{
return 2;
}

/////////////////////////////////////////////
Main.c
void Main ()
{
int tmp1 = Fun (); : Normal
int tmp2 = Fun_static (); : Connection Error

Getch ();
}