c - How do I use free() properly to free memory when using malloc? -

i have been using pointers , malloc , not know how use free() properly. have program allows user add record of data when select specific option. program allows function happen once , segfault. not think using free() , hoping point out problem. have global variables:

int records = 5; int access = 0;                  //initialize access counter 0 int count = 0;  struct childrensbook *first;    //initialize first pointer struct childrensbook *last;     //initialize last pointer struct childrensbook *temp;     //initialize temp pointer 

i have start of main function include predefined records:

int main(void) {     last = (struct childrensbook *) malloc(records * sizeof(struct childrensbook));     //allocate memory "last" pointer     first = last;             memcpy(last->title, "we're going on bear hunt", 27);                              //beginning of predefined records     memcpy(last->author, "michael rosen", 14);     last->price = 7.99;     last++;                                                                             //incrememnts pointer     count = count + 1;                                                                  //begins counting of records      memcpy(last->title, "goodnight moon", 15);     memcpy(last->author, "margaret wise brown", 20);     last->price = 8.99;     last++;                                                                             //incrememnts pointer     count = count + 1;                                                                  //adds 1 record count      memcpy(last->title, "one fish\n 2 fish\nred fish\n blue fish", 38);     memcpy(last->author, "dr. seuss", 10);     last->price = 8.99;     last++;                                                                             //incrememnts pointer     count = count + 1;                                                                  //adds 1 record count      memcpy(last->title, "snowmen @ night", 17);     memcpy(last->author, "caralyn buehner", 16);     last->price = 16.99;     last++;                                                                             //incrememnts pointer     count = count + 1;                                                                  //adds 1 record count      memcpy(last->title, "harold , purple crayon", 29);     memcpy(last->author, "crockett johnson", 17);     last->price = 6.99 

below menu loop have not included. problem lies in add function using free() here:

   addrecord()                                                                          //add function {                                                            last=first;                                                                         //get pointer in correct position     memcpy(&temp, &last, records *sizeof(struct childrensbook));                        //use memcpy copy info last temp      fprintf(stderr, "\nyou have added record:\n==========================\nbook: %s\nwritten by: %s\nprice: $%.2f\n", temp->title, temp->author,          temp->price);      temp++;      free(last);       //problem?? have tried using free(first), free(last) , free(temp) , none work....     count = count + 1;  }//end addrecord 

i have done way , still not work:

            addrecord()                                                                                     //add function     {                                                            last=first;                                                                         //get pointer in correct position     temp = (struct childrensbook *) malloc(records * sizeof(struct childrensbook));      memcpy(&temp, &last, records *sizeof(struct childrensbook));                        //use memcpy copy info last temp      fprintf(stderr, "\nyou have added record:\n==========================\nbook: %s\nwritten by: %s\nprice: $%.2f\n", temp->title, temp->author,          temp->price);      temp++;      free(last);     count = count + 1;  }//end addrecord 

last points first gets freed @ end of first call addrecord(). on second call crash since last no longer points allocated memory. but, more problematic not allocating new memory new record. see realloc().