C vs. C++

C++ is almost a complete superset of ANSI standard C, but there are differences.

In C++, these two function prototypes
```
int f();
```
and
```
int f(void);
```
are equivalent, note that void is optional.
In C++, all functions must have a protype. Protoypes are optional in C.
Only in C, is a character constant automatically elevated to an integer.
Only in C, may a global variable be declared more than once.
Only in C, may the main() be invoked from within the program.
Taking the address of a register variable is only allowed in C++