viod main()什么意思?
只用main()可以吗?

#include <stdio.h>
#include <math.h>
void main()
{
    int a,b,c;                                    // double a,b,c
    double s=(a+b+c)/2;                           //该处 S 以后的乘法S都为0；
    printf ("请输入三条边的长度:\n");
    scanf ("a=%2d b=%2d c=%2d\n",&a,&b,&c);          //scanf ("a=%d b=%d c=%d\n",&a,&b,&c);//
                                                      //s=(a+b+c)/2
    if(a+b>=c) printf("%lf",s=abs(s*(s-a)*(s-b)*(s-c)));
        else printf ("输入数据错误：两边之和必须大于第三边!\n");
    if(a+c>=b) printf("%lf",s=abs(s*(s-a)*(s-b)*(s-c)));
        else printf ("输入数据错误：两边之和必须大于第三边!\n");
    if(b+c>=a) printf("%lf",s=abs(s*(s-a)*(s-b)*(s-c)));   
        else printf ("输入数据错误：两边之和必须大于第三边!\n");

}

#include <stdio.h>
#include <math.h>
void main()
{
    double a,b,c,s;                                   
    printf ("请输入三条边的长度:\n");
   scanf ("a=%d b=%d c=%d\n",&a,&b,&c);
   s=(a+b+c)/2.0;
    if(a+b>=c) printf("%lf",s=abs(s*(s-a)*(s-b)*(s-c)));
        else printf ("输入数据错误：两边之和必须大于第三边!\n");
    if(a+c>=b) printf("%lf",s=abs(s*(s-a)*(s-b)*(s-c)));
        else printf ("输入数据错误：两边之和必须大于第三边!\n");
    if(b+c>=a) printf("%lf",s=abs(s*(s-a)*(s-b)*(s-c)));   
        else printf ("输入数据错误：两边之和必须大于第三边!\n");

}