iOS App Development Portable Genius

Composite C Data Types

C supports simple arrays. The initial values in an array are undefined, and the number of elements is a constant set at compile time.

int arrayOne[10];

//Creates an array of ten ints, arrayOne[0] to arrayOne[9]

//The initial values are undefined, and the number of elements is a constant

Use the struct keyword to create a composite data type made of fundamental data types. structs are rather like the ancestors of Objective-C’s objects. They’re simpler, they don’t support methods, and they don’t use Objective-C’s automatic memory management.

struct playerOne{

char name[20];

int xpos;

int ypos;

}

A union is like a struct and is defined in a similar way, but it can hold only a single value. In the following example, the union can hold a character array, an int called xpos, or an int called ypos. If you set one element in a union, the other elements become undefined. (This exotic behavior saves memory, but it’s largely unnecessary now.)

union playerOne{

char name[20];

int xpos;

int ypos;

}