Question

What is the difference between main in a C program and in a C++ program?

Other than

1. return statement ( default 1 in C,`0 in C++)

2. syntax:

   int main() { /* … */ }
   int main(int argc, char* argv[]) { /* … */ }
   int main() ,  void main() ,etc ...     
   

Mainly:

1. difference between main in C Program & C++ program

2. Are there any differences between C++98, C++03 and C++0x according to the ISO standard? i.e program’s entry point (program startup implementation), etc.

Answer 1

In modern C, and modern C++:

• main is always either int main() or int main(int, char*[]).
• In C89, you have to return from main explicitly.
• In C99 and C++, if you don’t return explicitly, you implicitly return 0.

[(I’ve checked the C99 standard now and edited this paragraph.)] For your second question, in C99 you must have precisely one of the two main functions. In C++ the standard says that a program is well-formed if it has a main function that returns int, and that every conforming implementation must accept the two listed versions as an entry point (for a “hosted program”, e.g. not for the Linux kernel); see 3.6.1. [/edit] To the best of my knowledge, calling conventions are also not part of the standard.

I don’t understand your question about memory, but do note that neither C99 nor C++03 have anything but a rudimentary memory model, whereas the new C++0x explicitly adds a memory model in order to enable well-defined concurrent and atomic operations.