Does main function have to have it datatype?

Answer 1

Though it gets compiled and runs but the compiler will warn about the lack of return type. So, yes it's better to be specified otherwise the compiler issues a warning (-Wreturn-type) like

"ISO C++ forbids declaration of 'main' with no type"

And having a warning is something smelly in a source code! 8D

Answer 2

"Can it have void return type"

In pre-standard C, yes. But as far as the standard concerns:

In C++
"It shall have a declared return type of type int [...]"

In C
"It shall be defined with a return type of int and with no parameters:
int main(void) { /* ... */ } "

Answer 3

Thanks

Answer 4

Can it have void return type