#include <stdio.h>
int main()
{
    int _ = 5, __ = 10, ___;
    ___ = _ + __;
    printf("%i\n", ___);
    return 0;
}

codeaft@codeaft:~$ gcc codeaft.c
codeaft@codeaft:~$ ./a.out
15
codeaft@codeaft:~$ 

#include <stdio.h>
int main()
{
    int a = 20;
    {
        int a = 40;
        // variables can have same name in different scope
    }
    printf("%d\n", a);
    return 0;
}

codeaft@codeaft:~$ gcc codeaft.c
codeaft@codeaft:~$ ./a.out
20
codeaft@codeaft:~$ 

#include <stdio.h>
void main()
{
    int x;
    x = 10, 20, 30;
    printf("%d\n", x);
}

codeaft@codeaft:~$ gcc codeaft.c
codeaft@codeaft:~$ ./a.out
10
codeaft@codeaft:~$