Structures are user-defined data types that group related variables together.
struct Person { char name[50]; int age; float height; };
struct Person person1; struct Person person2 = {"John", 25, 1.75};
strcpy(person1.name, "Alice"); person1.age = 30; person1.height = 1.65;
struct Person *ptr = &person1; ptr->age = 35; // arrow operator for pointer access
struct Address { char street[100]; char city[50]; }; struct Person { char name[50]; struct Address addr; };