class - Object initialization with 0 -

i wonder, happen if initialize object 0.

for example :

class vehicle { }  main() { vehicle v =0;  // or vehicle v; v=0; }

assuming c++, code generate compilation error @ least 4 reasons:

unlike k&r c, c++ not support functions implicit return values. main function returns int, , must explicitly declared such.
the class keyword not capitalized, , language case-sensitive. might typo, compiler won't care.
the declaration of vehicle class invalid. class declarations must end semicolon (after closing brace }).
the vehicle class not define constructor accepts integer (or implicitly convertible int), cannot initialize new vehicle object 0.

Roma