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Structures

Collection of one or more variable of different type.

Declaration

Use the struct keyword,

struct car {
  char brand[10];
  int year;
  int miles;
  double engine_size;
};
// or to use only car when declaring the object
typdef struct {
  int year;
  //...
} car;

Declaring a variable of type struct

// define a variable of type car
struct car mycar;
// or
car mycar;

// with assignation
car mycar = {"fiat", 2011, 79000, 100.3};

Accessing values

// field accessing
mycar.year = 2011;
mycar.miles = 50000;

mycar.year++;

Pointer to struct

car *carP = &mycar;

(*carP).year = 2012;
// or
carP->year = 2012;

Note that the -> operator is at the top of the precedence hierarchy with [] and ().

• So ++carP->year increments the year, not the pointer. Equivalent to ++(carP->year).
• *carP->brand dereferences the pointer brand, accessing the first letter of the brand.
• *carP->brand++ fetches the letter pointed, then increments the pointer.

It’s better to pass the reference of a structure to a function, rather than copying the whole object.

Dynamic allocation

struct car *mycar = malloc(sizeof(struct car));

// field accessing
(*mycar).year = 2011;
// or
mycar->year = 2011;