Do you give enough importance in writing main () in C language?

I am sure; you guys are quite familiar with C programming, especially, while it comes to write the first line of your main function. In my class, I have seen many of my students are writing main function with many different forms.

Some portion of students write like main(), some write main(void), again some of the students write void main(void) and int main(void). Now the question is which one is right?

All are right. Generally you write your C programs with Turbo C editor, or with any other, and generally they do not complain if you write any of them. But still, there is a factor of theoretical perfection. Trivial programming exercises may not be affected with whatever way you follow to declare main function, but in critical cases, your decision may make differences. This is why you should know which one is theoretically perfect.

As we always know that main is a function which gets called at the beginning of execution of any program. So like other functions, main must have a return type and it must expect arguments. If you are not calling your program (or your main likewise) from the command prompt, your main function should not bother for any arguments, so actually you should call your main with void argument, like main(void).

Now you may raise a point that main() itself suggest that no arguments are passed, so what is wrong with it? See one thing, in your current compiler, the default argument is void, but the same may not be true with other compilers or platforms. So you may end up with portability issues! Keep in mind, A GOOD PROGRAMMER NEVER RELY ON DEFAULTS. So please don’t rely on default things any more, clearly write that your main function is not expecting any arguments by writing main(void).

You already have an idea that a function can never work unless and until it is being called by any other program component. This is true for main also. The function main must be called by someone! Who is that? Who calls main function? It is the operating system who calls main function. Now the thing is, your operating system may decide to do any other job according to the success or failure of running your main function. It may so happen that if your program runs successfully, operating system will call a program P1, and if your program does not work, your operating system will call another program P2. So what if your operating system has no idea that your program did run actually or not? There lies the importance of return type of main. Your main function should return something to your operating system back to indicate whether it has ran successfully or not. The rule is if operating system gets an integer 0 back, it takes as main has ran successfully and any non zero value indicates the opposite. So your main program should return an integer. Hence you should write int main(void). Just to add with this, don’t forget to return 0 at the end of your main program so that, if all of your codes run successfully, your main function is capable of returning 0 to the operating system back, indicating that it was a success.

In this point you may argue, that your programs runs quite well even if you do not provide return type to main and you just write main(void). How come it is possible?

Once again, at your age, you are writing just some of trivial academic codes. The situations here are not such critical that your operating system may decide any other thing depending on the success or failure of your main(). But, in near future, you are to write such critical programs, so get prepared from now.

Cool, so to conclude, int main(void) is perfect to write and I encourage you to write like that along with a return 0 at the last line.