#include<stdio.h>
void main()
#define PI 3.1415926;
{
    int a,b,c,d,t;
    double e,f,g;
    printf("绕的圈数为:");
    scanf("%d",&a);
    b=12/0.38;c=a%b;d=a/b;
    if (a>b)
    {for(t=d,e=0;t!=0;t--)
        {
            f=13*PI*b+0.38*d*PI*b;
            e=e+f;
        }
        g=13*c*PI+0.38*++d*PI*c;
        e=e+g;
        printf("线长为:%lf",e);}
    else if(a<=b)
        e=a*PI*12.8;
    printf("线长为:%lf",e);
}

关于illegal indirection的疑问，希望能得到解答
#include<stdio.h>
void main()
#define PI 3.1415926;
{

应该改为
#include<stdio.h>
#define PI 3.1415926
void main()

{

或者直接去掉冒号~~
关于illegal indirection的疑问，希望能有解答
#include<stdio.h>
void main()
#define PI 3.1415926;==》#define PI 3.1415926
{
    int a,b,c,d,t;
    double e,f,g;
    printf("绕的圈数为:");
    scanf("%d",&a);
    b=12/0.38;c=a%b;d=a/b;
    if (a>b)
    {for(t=d,e=0;t!=0;t--)
        {
            f=13*PI*b+0.38*d*PI*b;
            e=e+f;
        }
        g=13*c*PI+0.38*++d*PI*c;
        e=e+g;
        printf("线长为:%lf",e);}
    else if(a<=b)
        e=a*PI*12.8;
    printf("线长为:%lf",e);
}

改过来对了！！谢谢指点！！