Optimizing bio_display()

Here is the source code:

void bio_display(const char *str, int row, int col, int len){
  bio_move(row, col);
  if(len <= 0){
    bio_putstr(str);
  }
  else{
    int i;
    for(i=0; i< len && str[i];i++){
      bio_putch(str[i]);
    }
    for(;i< len;i++){
      bio_putch(' ');
    }
  }
}

To optimize it, I got this solution :

void bio_display(const char *str, int row, int col, int len) {
    bio_move(row, col);
    if( len <= 0)
        bio_putstr(str);
    else {
        for(;len>0; len--) bio_putch(*str ? *str++ : ' ' );
    }
}

From the same logic, it also can be shortened as:

void bio_display(const char *str, int row, int col, int len) {
   for((bio_move(row, col), (len <= 0)?bio_putstr(str):0);  len>0;   len--)
       bio_putch(*str ? *str++ : ' ' );
} 

I tried to use bio_putstr() instead of bio_putch() which Farad mentioned in the class, but considered the length of the string I insisted to use bio_putch().