Code

 Header...
// Return the scalar (dot) product of two vectors
 float dotprod(const float v1[],const float v2[],int n){
   ... 

»  float res=0;

»  for ( int i=0;i<n; ++i) 
    res+=v1i*v2i;

»  return res;
}

#define VECLEN 2
#define NVECS 3
 int main(){
   ... 

»  float dot[NVECS][NVECS], vector[NVECS][VECLEN]=
    {1.5,3.9,4.7,7.2,2.1,5.13,};
»  int j, k;

»  for (j=0; j<NVECS; ++j) {
»    for (k=j; k<NVECS; ++k) 
      dot[j]k=dotprod(vectorj, vectork, VECLEN);
  }

»  return 1;
}