#include<stdio.h>
typedef struct complex{
    double r;
    double i;
    }COMPLEX;
COMPLEX *fun1(COMPLEX ,COMPLEX );
COMPLEX *fun2(COMPLEX ,COMPLEX);
COMPLEX *fun3(COMPLEX ,COMPLEX );
COMPLEX *fun4(COMPLEX ,COMPLEX );
int main()
  {
    COMPLEX a,b,c,d,f,e;
    scanf("%d %d %d %d",&a.r,&a.i,&b.r,&b.i);
  c=*fun1(a,b);
  d=*fun2(a,b);
  e=*fun3(a,b);
  f=*fun4(a,b);
    printf("(%+.2lf+%+.2lfi)+(%+.2lf+%+.2lfi)=(%+.2lf+%+.2lfi)",a.r,a.i,b.r,b.i,c.r,c.i);
    printf("(%+.2lf+%+.2lfi)-(%+.2lf+%+.2lfi)=(%+.2lf+%+.2lfi)",a.r,a.i,b.r,b.i,d.r,d.i);
    printf("(%+.2lf+%+.2lfi)+(%+.2lf+%+.2lfi)=(%+.2lf+%+.2lfi)",a.r,a.i,b.r,b.i,e.r,e.i);
    printf("(%+.2lf+%+.2lfi)+(%+.2lf+%+.2lfi)=(%+.2lf+%+.2lfi)",a.r,a.i,b.r,b.i,f.r,f.i);
    return 0;
  }

  COMPLEX *fun1(COMPLEX a,COMPLEX b )
  {
      COMPLEX *S;
      S->r=a.r+b.r;
      S->r=a.i+b.i;
      return S;
  }
  COMPLEX * fun2(COMPLEX a,COMPLEX b )
  {
      COMPLEX *S;
      S->r=a.r-b.r;
      S->i=a.i-b.i;
      return S;
  }
  COMPLEX * fun3(COMPLEX a,COMPLEX b )
  {
      COMPLEX *S;
      S->r=a.r*b.r-b.i*a.i;
      S->i=a.i*b.r+a.r*b.i;
      return S;
  }
  COMPLEX * fun4(COMPLEX a,COMPLEX b )
  {
      COMPLEX *S;
      S->r=(a.r*b.r+b.i+b.i)/(b.r*b.r+b.i*b.i);
      S->i=(a.i+b.r-a.r*b.i)/(b.r*b.r+b.i*b.i);
      return S;
  }

  COMPLEX fun1(COMPLEX a,COMPLEX b )
  {
      COMPLEX S;
      S.r=a.r+b.r;
      S.i=a.i+b.i;
      return S;
  }
如果要用指针，函数内部请malloc

2楼的程序有问题哦！！！COMPLEX S;定义的是一个结构体局部变量，结构体变量名就相当于一个指向结构体初始地址的指针，return S;返回的是一个地址哦！！！！不是返回结构体数据的，这个数据在退出该函数的时候已经释放掉了

这是在引用楼主的代码。。。