Code (Linked List code from a Help Session)

// one of the basic bits of a linked list is the node

#include <stdlib.h>
#include <assert.h>
#include <stdio.h>

struct linkedList {
    // this pointer aims at the first element of the list
    struct node *head;
};

struct node {
    // this pointer links the chain of nodes together
    struct node *next;
    // the data is the information that we're storing
    int data;
};

// These functions could be declared in a header file, I'm just working
// in one file for now
void addElementAtEnd(struct linkedList *list, int item);
void printList(struct linkedList *list);

int main() {
    // myList is a pointer aiming at a linkedList struct in memory
    struct linkedList *myList = malloc(sizeof (struct linkedList));
    // setting this to NULL makes 100% sure this looks empty at the beginning
    myList->head = NULL;
    
    // Now that we have an empty list, we want to add some elements
    // We're going to add elements to the tail end of the list
    addElementAtEnd(myList, 1);
    addElementAtEnd(myList, 2);
    addElementAtEnd(myList, 3);
    printList(myList);
}

// Find the last element of the list, add a new node after it
void addElementAtEnd(struct linkedList *list, int item) {
    // loop until the end of the list to find where to add the node
    struct node *loopingNode = list->head;
    struct node *previousNode = NULL;
    
    // stopping case: we stop looping when the node we're looking at is NULL
    while (loopingNode != NULL) {
        
        // Keep track of the node before the current one
        previousNode = loopingNode;
        
        // increment . . . move from one node to the next
        loopingNode = loopingNode->next;        
    }
    // when this loop finishes,
    // loopingNode will be NULL
    // previousNode will be the last node
    
    // We've been asked to add to the end of the list, and now
    // we know exactly where that is
    
    // Now we add a node after the "previousNode" called "newNode"
    struct node *newNode = malloc(sizeof (struct node));
    // assert will be ignored if it's true
    // if what's in the brackets is false, the program will stop here
    // and report back where the failure was
    // This assert is checking whether the malloc above succeeded
    assert(newNode != NULL);
    
    // now populate the node. It's next is NULL because it's at the end
    // of the list
    newNode->next = NULL;
    newNode->data = item;
    
    // If the list was empty before we added this node
    // This node becomes the first node in the list, so it should be
    // the new head
    if(list->head == NULL) {
        list->head = newNode;
    } else {
        // The list already had at least one element
        // connect this node to the rest of the list
        // this is done by connecting previousNode's next to this newNode
        previousNode->next = newNode;
    }    
}

// Print out all the elements of the list
void printList(struct linkedList *list) {
    // This is a very standard while loop for looping through all the elements
    // We're going to use this to print out each element
    struct node *loopNode = list->head;
    while(loopNode != NULL) {
        printf("%d\n", loopNode->data);
        loopNode = loopNode->next;
    }
}