dynamic link in C

can anyone please help me.
i really can't understand the logic of this program.
i just want to know your opinion by visualy inspecting the code.
because i really can't understand the for loop part downwards.
please help and explain. thanks.

Code:

#include "stdio.h" /* this is needed only to define the NULL */
#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 */
}

The first thing to do is to add some indentation to that code. I ran your code through indent with default options and then through codeform:

Code:

#include "stdio.h"		/* this is needed only to define the NULL */
#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 ("&#37;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 */
}

[edit] Okay, now I can read it.

malloc() shouldn't be casted, and <stdlib.h> should be included so that without the cast you don't get a warning.

You should also include <string.h>, because of strcpy().

Also see MacGyver's post below. [/edit]

Unless you copied it incorrectly, whoever wrote this program needs to learn a thing or two about proper indention. Also, they could stand to learn a lesson about writing correct, portable code.

All they are doing is allocating memory for a linked list, inserting, printing, and deleting nodes. I'm guessing you just want help on linked lists for the most part:

http://en.wikipedia.org/wiki/Linked_list
http://www.cprogramming.com/tutorial/c/lesson15.html