Introduction to 64-Bit Transition Guide For Cocoa

OS X is undergoing a gradual transition to a 64-bit model. An 64-bit executable is a process that can support a 64-bit address space. In a 64-bit world pointers are 64 bits (eight bytes) and some integer types, once 32 bits, are now 64 bits. These fundamental changes required for 64-bit processes impact the programmatic interfaces of many of the frameworks of OS X, including Cocoa, in various ways.

This document explains the rationale for the 64-bit transition and describes the 64-bit related changes to the Cocoa API. It also discusses the steps you must take to convert existing Cocoa applications to a 64-bit model.

Organization of This Document

This document has the following chapters:

• Moving to 64-Bit Addressing provides background information about the 64-bit initiative for OS X and offers general advice for developers thinking about moving their Cocoa projects to 64-bit addressing.

• 64-Bit Changes To the Cocoa API describes the changes to data types for integers, floating-point values, enumeration constants, and other types of values in the Cocoa API.

• Converting an Existing Application to 64-Bit explains how to run the script for converting a Cocoa code base to 64-bit and describes modifications you may have to perform manually after the script is run.

• Optimizing Memory Performance describes common memory usage patterns in 64-bit applications and how to profile your application to find them.