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

Question

I'm a Linux user who started learning C and I'm trying to compile this source that I typed:

#include <stdio.h>
main()
{
        float c,d;
        c = 10215.3;
        d = c / 3;
        printf("%3.2f
",d);
        return 0;
}

It compiled with this using a makefile that I wrote:

cc -Wall -g     printf.c   -o printf

but I'm getting this warning:

printf.c:2:1: warning: return type defaults to ‘int’ [-Wreturn-type]

it compiles the code and I get the desired output but I want to understand what this means

Answer 1

main()

should be

int main()

In C89, the default return type is assumed to be int, that's why it works.