Differences of C and C++ Could you write a small program that will compile in C but not in C++ ?

Differences of C and C++ Could you write a small program that will compile in C but not in C++ ? 

In C, if you can a const variable e.g. 
const int i = 2; 
you can use this variable in other module as follows 
extern const int i; 
C compiler will not complain. 

But for C++ compiler u must write 
extern const int i = 2; 
else error would be generated.