Thread: Linked list source code errors

I have been using an online C tutorial to study C. The tutorial is ctutor.pdf, by Tim Ward, which can easily be found online. I'm currently studying Linked lists. The example code seems to have logical errors, which I'm not capable of correcting because I'm new to the concept.

Could someone find these errors and correct them for me and repost the source code for me to study?

Here is the code:

Code:

#include <stdio.h>
#include <string.h>
#define RECORDS 6

main( )
{
  struct animal {
    char name[25]; /* The animals name */
    char breed[25]; /* The type of animal */
    int age; /* The animals age */
    struct animal *next; /* a pointer to another record of this type */
  } *point, *start, *prior; /* this defines 3 pointers, no variables */
int index;

/* the first record is always a special case */
  start = (struct animal *)malloc(sizeof(struct animal));
  strcpy(start ->name,"general");
  strcpy(start ->breed,"Mixed Breed");
  start->next = NULL;
  prior = start;

  /* a loop can be used to fill in the rest once it is started */
  for (index = 0;index < RECORDS;index++) {
    point = (struct animal *)malloc(sizeof(struct animal));
    strcpy(point->name,"Frank");
    strcpy(point->breed,"Laborador Retriever");
    point->age = 3;
    point->next = point; /* point last "next" to this record */
    point->next = NULL; /* point this "next" to NULL */
    prior = point; /* this is now the prior record */
  }

  /* now print out the data described above */
  point = start;
  do{
    prior = point->next;
    printf("%s is a %s,and is %d years old.\n", point->name,
    point->breed, point->age);
    point = point->next;
  } while (prior != NULL);

  /* good programming practice dictates that we free up the */
  /* dynamically allocated space before we quit */
  point = start; /* first block of group */
  do{
    prior = point->next; /* next block of data */
    free(point); /* free present block */
    point = prior; /* point to next */
  } while (prior != NULL); /* quit when next is NULL */

  getch();
}

Also, I would appreciate if someone could link me to some useful resources that explain Linked lists. A Linked list is the most difficult programming concept yet. =[

Thanks.

~Billy

Code:

    point->next = point; /* point last "next" to this record */
    point->next = NULL; /* point this "next" to NULL */

It looks like this should be:

Code:

    prior->next = point; /* point last "next" to this record */
    point->next = NULL; /* point this "next" to NULL */

I haven't tested the code or anything, but I can definitely tell you the original two lines are definitely not correct.