Not declaring a function's return value is an error in C++, whether the function is main or not. In C99, the October 1999 revision to Standard C, not declaring a function's return value is also an error (in the previous version of Standard C an implicit int was assumed as the return value if a function was declared/defined without a return value). But the usual requirement of both Standard C++ and Standard C is that main should be declared to return an int. In other words, this is an acceptable form of main:

The problem is that this code declares main to return a void and that's just no good for a strictly conforming program. Neither is this:

implicit int not allowed in C++ or C99


Hope this helps,
- Stack Overflow

Operating systems such as UNIX require applications to return an integer value.
0 usually meaning success and non-zero meaning an error.

In this reply, I posted 6 links to explanations of why it is considered wrong.

the first, you mustn't have any return statement in your main() function as if you use void main() declare. If you use int main() function, you must return a int value, otherwise your complier will prompt a warning.

In You Program You can Have Program like this

pro 1
void main()
{
/* */

}

pro 2

int main()
{

/* */

return 0;
}

in pro1 its showing you void main it's mean's RETURN NOTHING just a main Function with your code!! but in pro2 its haveing int main() function it's mean's that function return a value!! so if you put in void main function to return a value u will get an Error so best way is you have to use void main function in your program!!

example

#include <stdio.h>
#include <conio.h>


int call(int x,int y);

void main()
{
int num1,num2,ans;

clrscr();
printf("Enter the First number : ");
scanf("%d",&num1);
printf("\nEnter the Secound Number : ");
scanf("%d",&num2);

/*call the cal function using ans */

ans=call(num1,num2);

printf("The Add of num1 and num2 is %d",ans);

getch();
}

int call(int x,int y)
{
int z;

z=(x+y);

return (z); /* cal function go back to main function*/

}

People please! Is this a hosted implementation? Do you excect printf to do anything? Then void main is incorrect. Period.

Why is it necessary to have void main() in Java? Any takers?

>Why is it necessary to have void main() in Java?
I'd say it's because Java applications run in a virtual environment, curtosey of the Java VM. So when a program finishes, it doesn't return to the operating system, it in fact returns to the VM. Therefore rules such as int main do not apply.

void main()

{

unsigned int i=65537;

float j=2.25;

printf("%d",i*j);

getch();

}