Structures

Sometimes you need to group related data together — a student has a name, an age, and a grade. Instead of juggling separate variables, C lets you bundle them into a structure using struct.

Defining a Struct

A struct is a blueprint for a composite type. You define it once, then create variables that have all those fields together.

#include 
#include 
struct Student {
  char name[50];
  int age;
  float grade;
};
int main() {
  struct Student s1;
  strcpy(s1.name, "Alice");
  s1.age = 20;
  s1.grade = 92.5;
  printf("%s is %d years old with grade %.1f\n", s1.name, s1.age, s1.grade);
  return 0;
}
    

The Arrow Operator (->)

When you have a pointer to a struct, use -> instead of . to access members. It's shorthand for dereferencing then dotting: (*ptr).member becomes ptr->member.

#include 
struct Point {
  int x;
  int y;
};
int main() {
  struct Point p1 = {3, 7};
  struct Point *ptr = &p1;
  printf("(%d, %d)\n", ptr->x, ptr->y);
  ptr->x = 10;
  ptr->y = 20;
  printf("(%d, %d)\n", ptr->x, ptr->y);
  return 0;
}
    

Nested Structures

You can put a struct inside another struct. Great for modeling real-world relationships, like an address inside a person.

#include 
#include 
struct Address {
  char street[100];
  char city[50];
};
struct Person {
  char name[50];
  struct Address addr;
};
int main() {
  struct Person p;
  strcpy(p.name, "Bob");
  strcpy(p.addr.street, "123 Main St");
  strcpy(p.addr.city, "Springfield");
  printf("%s lives at %s, %s\n", p.name, p.addr.street, p.addr.city);
  return 0;
}