static keyword keeps the scope of a global variable limited to that translation unit.
If I use static int x in a .h file and include that .h file every other file, won't they all belong to the same translation unit?
Then, won't x be visible everywhere?
So what is the role of static now?
Also, is there any use of static const int x ,where x is a global variable?
Aren't all const global variables static by default?
And is a const variable's scope limited to the TU even if it confined in a for loop in the file?
If you write
static const int x
in an .h file then every translation unit that #include-s this .h will have its own private variable x.
If you want to have 1 global variable visible to everyone you should write
extern const int x;
in the .h file and
const int x = ...;
in one of the .cpp files.
If you want to have a static const int visible to just one translation unit - don't mention it in the .h files at all.