The variables you declare in Objective-C, Objective-C data types, must be a type that the compiler can recognize. Objective-C comes with a number of built-in data types, as well as mechanisms to create new ones, for programming your iPhone or Mac OS X applications.

Built-In Types
Type Description Size
char A character 1 byte
int An integer — a whole number 4 bytes
float Single precision floating point number 4 bytes
Double Double precision floating point number 8 bytes
short A short integer 2 bytes
long A double short 4 bytes
long long A double long 8 bytes
BOOL Boolean (signed char) 1 byte

Enumeration types

enum  typeName { identifier1, ... identifiern};
Identifiers are of constants of type int.


typedef  typeName  identifier;
Associates an identifier with a specific type.


const type  identifier  = value;
#define identifier value
Allows you to define names for constants.