void main() function,it will flow of the program 
execution,what are the next step of line to execute.
for example,
void main()
{
int b=0
cout<<b;
int c=0;
cout<<c;
}
/*it will indicate first create object of int type,after it 
will genereate next statement.*/

void main()
//this function indicate the starting of the program furthur
tells that it has non return value.

main is the special function,,,,,,,, wch contain the 
defination of u r program or we can say it contain the main 
body of u r program.It is called as special funtion becoz 
it is invoked by the compiler itself,no any other function 
call the main().
the void is a return type which is use when no meaning ful 
value is to be return

it has no meaning it does not return any value to the 
operating system