What is the correct way to create the Main function in C?

The function maincan only be written in two ways in c :

int main(void)
{
   ...

   return 0;
}

int main(int argc, char **argv)
{
   ...

   return 0;
}

Any other way is not standard.

TLDRs;

First of all, let's remember how is the definition of a function in c, that at the end of the day, mainit is nothing more than the main function

tipo_resultado nombre_function(tipo_param1 param1, tipo_param2 param2, ... ) {
    ...
}

To see an example we will run this small program

#include <stdio.h>
int testear() {
    int variable = 8;
    return variable;
}

int main()
{
    printf("%i", testear());
}

If we run the program we can see that it will print 8. Since we have declared that the function testearis going to return a int.

Functions int, if they are not assigned a return value, return default0. Let 's see

#include <stdio.h>
int testear() {
    int variable = 8;
}

int main()
{
    printf("%i", testear());
}

In this example we see that even if we don't pass any to it, it returnprints 0. Since, as mentioned, it is the default value for functions in return int.

Now what happens if we don't define the type, that is, as follows.

#include <stdio.h>
testear() {
    int variable = 8;
}

int main()
{
    printf("%i", testear());
}

We can see that this returns a 0anyway, since the default return variable type is a int. however we can notice here the followingwarning

 warning: return type defaults to ‘int’ [-Wimplicit-int]

This is because it advises against not returning a return variable, in ccauses only a warning, and in c++causes an error.

Now what if we don't want to return a return variable

#include <stdio.h>
void testear() {
    int variable = 8;
    printf("%i", 8);
}

int main()
{
    testear();
}

We can define voidthat it means that the function does not return any value. In fact if we try to do the following.

#include <stdio.h> void test() { int variable = 8; printf("%i", test()); }

int main()
{
    printf("%i", testear());
}

We can notice the error, since it testeardoesn't return any value.

ABSTRACT

In cis used int main(){return 0;}and the return number means whether your program executed properly, leaving 0 as ejecución correctaor returning another numeric value indicating that the execution failed at something.

main(){...}returns the same as int main(){return 0;}given that if no return type is defined in a function the return value type is intby defaultand the value by defaultfor functions intwhen not explicitly declared is 0. However it is discouraged not to define return value type in a function. You can use void main(){...}it if you don't want to declare a return variable in your function main, however also in several places like in this article they mention that according to the ANSI standard Cit shouldn't be used void main(){...}so the best option is to always useint main(){}