```d
extern(C) int main()
{
import core.stdc.stdio;
string hello = "hello";
printf(hello.ptr);
return 0;
}
```
1) You forgot to import ``core.stdc.stdio``
2) String literal is of type string (which is an alias to
``immutable(char)[]``).
3) A slice is a pointer + length, and C doesn't understand slices, so
you must explicitly pass in the pointer from the slice (the compiler
would do this for you if you had the literal in the arguments list
instead of the variable).
