linked-list-dynamic-mem-initialization.c

#include <stdio.h>
#include <stdlib.h> // this is for calloc

typedef struct node {
  int x,y;
  struct node *next;
} Node;

int main() {
  /*
   * calloc allocates memory and initializes it
   * the allocation happens in heap
   */
  Node *head = (Node*)calloc(1, sizeof(Node));
  /*
  * We're accessing x through pointer, therefore we must use '->' syntax
  */
  head->x = 10;
  head->y = 15;
  head->next = NULL;

  printf("%d %d\n", head->x, head->y);
  return 0;
}

print-1-n-recursion.c

#include <stdio.h>

void print(int n) {
  /*
   * This is base case
   * triggers when n = 0
   */
  if (n < 1) return;

  /*
   * This is recursively calling itself where n is reducing by one every time
   */
  print(n - 1);
  printf("%d ", n);
}

int main() {
  /*
  * This is user defined
  */
  int n;
  scanf("%d", &n);
  print(n);

  return 0;
}

struct-access-using-pointer.c

#include <stdio.h>

typedef struct node {
  int el;
} Node;

int main() {
  Node node;
  /*
  * This is a pointer that holds the memory address of Node
  * Therefore it points to the Node instance called node
  */
  Node *node_ptr = &node;

  node.el = 9;

  /*
  * This should print out 9 as we've assigned 9 to the el
  */
  printf("%d\n", node.el);
  /*
  * As node_ptr points to the original instance, it should also print 9
  */
  printf("%d\n", node_ptr->el);

  /*
  * This changes the original instance
  */
  node.el = 5;
  /*
  * As it points to the memory and doesn't just hold any value
  * changes to the original one reflects when accessing through pointer
  * therefore it prints 5 as well
  */
  printf("%d\n", node_ptr->el);

  return 0;
}

struct-multiple-records.c

#include <stdio.h>
#include <string.h>

typedef struct book {
  char title[50];
  char author[50];
  char subject[100];
  int id;
} Book;

int main() {
  Book book1, book2;

  /*
  * Book 1 details
  */
  strcpy(book1.title, "Surrounded by Idiots");
  strcpy(book1.author, "Thomas Erikson");
  strcpy(book1.subject, "Human Behavior and Personality Analysis");
  book1.id = 26012201;

  /*
  * Book 2 details
  */
  strcpy(book2.title, "Life 3.0");
  strcpy(book2.author, "Max Tegmark");
  strcpy(book2.subject, "Artificial Intelligence and the Future");
  book2.id = 26012202;

  /*
  * Print book 1 info
  */
  printf("Book 1 title : %s\n", book1.title);
  printf("Book 1 author : %s\n", book1.author);
  printf("Book 1 subject : %s\n", book1.subject);
  printf("Book 1 id : %d\n", book1.id);

  /*
  * Print book 2 info
  */
  printf("Book 2 title : %s\n", book2.title);
  printf("Book 2 author : %s\n", book2.author);
  printf("Book 2 subject : %s\n", book2.subject);
  printf("Book 2 id : %d\n", book2.id);

  return 0;
}