references/C/4_structures.md

Structures

A collection of variables that create a new type, like classes/objects, but pure data.

Keep related variables and values together.

typedef struct Pixel{
	float X;
	float Y;
}

Declared as any other variable type

Pixel p;

With initialisation

Pixel p = {10.0f, 25.0f};

If typedef not before the original struct, it'll need to be added. Structs are in a different namespace.

struct Pixel p;

You can assign and access members of the declared structs using a .

float x_value = p.X;

p.Y = 66.0f;

Layout and Padding

C and C++ compilers require values in structs to be in order of sizeof, so shorts before ints, etc. If this isn't the case the struct will take up more memory that needed. eg.

short x; // 2 bytes, with 2 bytes of padding
int y; // 4 bytes, no padding 
short z; // 2 bytes, 2 bytes of padding
// total 12 bytes

short x; // 2 bytes
short z; // 2 bytes 
int y; // 4 bytes
// total 8 bytes