pointer problems, help!

[Terry Mitchem]

        I am having some major problems getting a piece of code to work.
It seems that everytime I change the contents of one string, it affects
another one. For example, when I build the filename below, it gets wiped
out when I null the members of "target_player". The code is below, and below
that is the datafile I am using.

void edit_category()
{
  struct
  {
    char *card_number;
    char *quantity;
    char *first_name;
    char *last_name;
    char *price_mint;
    char *price_ex;
  } target_player;

  char filename[80],carriage_return[5];
  int infile,bytes;

  *filename=NULL;

  strcat(filename,".\\"); strcat(filename,category.brand);
  strcat(filename,"\\");  strcat(filename,category.type);
  strcat(filename,"\\");  strcat(filename,category.year);
  strcat(filename,"\\");  strcat(filename,category.other);
  strcat(filename,"\\data");

  *target_player.card_number=NULL; *target_player.quantity=NULL;
  *target_player.first_name=NULL; *target_player.last_name=NULL;
  *target_player.price_mint=NULL; *target_player.price_ex=NULL;

  infile=open(filename,O_RDONLY);
  if (infile==-1) exit(1);

  read(infile,target_player.card_number,5);
  read(infile,target_player.quantity,3);
  read(infile,target_player.first_name,21);
  read(infile,target_player.last_name,21);
  read(infile,target_player.price_mint,7);
  read(infile,target_player.price_ex,7);
}
----------------------------------------------------------------------------
Here is the datafile:

8    2  joe                  montana              .75    .40
9    2  christian            okoye                .20    .10    

        Any and all help is appreciated. I don't seem to be able to get
anything useful out of K&R to help me. I am compiling with turbo-c.
                        Thanks in advance
                                Terry