C++ - Static Globals/Static Private Members?

[MaximLaHaxim]

Hey there. Now, I know that "static" in a C++ class means that the var you're declaring can be accessed in a similar fashion to a namespace, e.g

class MyTest
{
        public:
                static int test = 5;
};

int main()
{
        std::cout << MyTest::test;
}

However, there are two other uses I've seen with 'static' that don't really make sense, at least with my current understanding.

1. The use of a global static, e.g

static int somerandomvar = 2;
int main()
{ std::cout << "wat?"; }

2. The use of a static private member in a class/struct.

struct test
{
        private:
                static int test = 5;
};

What do both of these uses of it mean?

[Silverlan]

[QUOTE=MaximLaHaxim;49619427]
1. The use of a global static, e.g

static int somerandomvar = 2;
int main()
{ std::cout << "wat?"; }

[/QUOTE]
'static' makes sure the variable is only valid for the cpp it was defined in. For a non-static global variable, you can do stuff like:

main.cpp:

int somerandomvar = 2;
void print_some_random_var();

int main(int,char*[])
{
	print_some_random_var();
	for(;;);
	return EXIT_SUCCESS;
}

other.cpp:

#include <iostream>

extern int somerandomvar;
void print_some_random_var()
{
	std::cout<<somerandomvar<<std::endl;
}

This would print '2'. If 'somerandomvar' is static, however, you'll get an unresolved external, because it can't find the source for 'somerandomvar' in 'other.cpp'.
Basically, non-static global variables can be shared between cpps, static global variables can't.

[QUOTE=MaximLaHaxim;49619427]2. The use of a static private member in a class/struct.

struct test
{
        private:
                static int test = 5;
};

[/QUOTE]

You could use it for example to keep track of the number of objects that exist of your class at any time:

#include <iostream>

class MyTest
{
private:
	static int COUNT;
public:
	MyTest();
	~MyTest();
};

int MyTest::COUNT = 0;

MyTest::MyTest()
{
	++COUNT;
	std::cout<<"There are "<<COUNT<<" objects of type '"<<typeid(*this).name()<<"'"<<std::endl;
}

MyTest::~MyTest()
{
	--COUNT;
}

int main(int,char*[])
{
	MyTest a,b,c,d,e,f;
	for(;;);
	return EXIT_SUCCESS;
}

This is pretty much the only case I can think of where I've used a static private, but I'm sure there are others.