s it fine to write “void main()” or “main()” in C/C++?

• Difficulty Level : Easy
• Last Updated : 12 Jul, 2021

The definition

• CPP

void main()

{ /* ... */ }

is not and never has been C++, nor has it even been C. See the ISO C++ standard 3.6.1[2] or the ISO C standard 5.1.2.2.1. A conforming implementation accepts

• CPP

int main()

{ /* ... */ }

and

• CPP

int main(int argc, char* argv[])

{ /* ... */ }

A conforming implementation may provide more versions of main(), but they must all have return type int. The int returned by main() is a way for a program to return a value to “the system” that invokes it. On systems that don’t provide such a facility the return value is ignored, but that doesn’t make “void main()” legal C++ or legal C. Even if your compiler accepts “void main()” avoid it, or risk being considered ignorant by C and C++ programmers. 
In C++, main() need not contain an explicit return statement. In that case, the value returned is 0, meaning successful execution.

For example: 

• CPP

#include <iostream>

int main()

{

    std::cout

        << "This program returns the integer value 0\n";

}

Note also that neither ISO C++ nor C99 allows you to leave the type out of a declaration. That is, in contrast to C89 and ARM C++, “int” is not assumed where a type is missing in a declaration. 

Consequently:

• CPP

#include <iostream>

main()

{ /* ... */}

The above code has no error. If you write the whole error-free main() function without a return statement at the end then the compiler automatically adds a return statement with proper datatype at the end of the program.
Source: http://www.stroustrup.com/bs_faq2.html#void-main
To summarize the above, it is never a good idea to use “void main()” or just “main()” as it doesn’t confirm standards. It may be allowed by some compilers though.
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