no we can write a program with out main function, this 
function is the main function which usually help OS to kill 
the process that has executed, like in JAVA main() is used 
as a thread whose wqork is to kill the executed process and 
mark those as GC( Garbage collection)

no we can't write a program with out main function, this 
function is the main function which usually help OS to kill 
the process that has executed, like in JAVA main() is used 
as a thread whose wqork is to kill the executed process and 
mark those as GC( Garbage collection)

as for i know in C , we cant write a program wit out main()..
since whatever function we write (user defining functions).
it will start executing the statements only from the
main().... so only we will say tht FIRST EXECUTABLE FUNCTION
IS THE MAIN() FUNCTION.........

I think its possiblle through macros ....like this

 #define main() start
  start
{
printf("Hai");
}

no because every c prog. can compile from main function.
but when we write a code for creating a header file, we 
cant use main function.

no we cant write bcoz main() tells to the processor that it 
is starting of the c programming

@Rahul
In java, the job of killing the threads who have done their job (and garbage collection) is done by the java runtime environment. The main thread may even itself come to an end before all its child threads have completed their execution.

Yes we can,try it
class d
{
static{
System.exit(0);
}
}
it compiles and executes without error in java.

yes, we can write C programs , without main() functions.
though they are not the kind of programs we use in everyday
life .For example linux kernel source code do not have any
main() function.

for details u can visit :

http://samarthonweb.blogspot.com/2009/08/c-programe-with-no-main-function.html