Introduction to Memory Management

Overview

This chapter is a general introduction to memory management on Macintosh computers. It describes how the Operating System organizes and manages the available memory, and it shows how you can use the services provided by the Memory Manager and other system software components to manage the memory in your application partition effectively.

You should read this chapter if your application or other software allocates memory dynamically during its execution. This chapter describes how to

• set up your application partition at launch time
• determine the amount of free memory in your application heap
• allocate and dispose of blocks of memory in your application heap
• minimize fragmentation in your application heap caused by blocks of memory that cannot move
• implement a scheme to avoid low-memory conditions

You should be able to accomplish most of your application's memory allocation and management by following the instructions given in this chapter. If, however, your application needs to allocate memory outside its own partition (for instance, in the system heap), you need to read the chapter " Memory Manager " in this book. If your application has timing-critical requirements or installs procedures that execute at interrupt time, you need to read the chapter "Virtual Memory Manager" in this book. If your application's executable code is divided into multiple segments, you might also want to look at the chapter "Segment Manager" in Inside Macintosh: Processes for guidelines on how to divide your code into segments. If your application uses resources, you need to read the chapter "Resource Manager" in Inside Macintosh: More Macintosh Toolbox for information on managing memory allocated to resources.

This chapter begins with a description of how the Macintosh Operating System organizes the available physical random-access memory (RAM) in a Macintosh computer and how it allocates memory to open applications. Then this chapter describes in detail how the Memory Manager allocates blocks of memory in your application's heap and how to use the routines provided by the Memory Manager to perform the memory-management tasks listed above.