What does this do ?

[paulpliviu]

What does this do ?
int Next_operator(char* expr, unsigned long length, unsigned long& currpos, char* Operator)..the highlighted things

if( ::isdigit(expr[currpos]) )....the 4 points..

[bbgst]

1) if you mean pointers: http://cplusplus.com/doc/tutorial/pointers/
2) it's the scope operator. If you supply a class on the right size, it returns the left side on its scope. So:

class A
{
	public:
		int a;
};

To access the a variable from class A, you use A::a. Without anything on the right side, its effect is returning the left side on the global scope:

int a;

class A
{
	public:
		int a;
		int f() { ::a++; }
};

Without using ::, there is no way you could access the global a.

[paulpliviu]

the program i'm refering to does not involve classes and objects...

[modoran]

It refers to global namespace.