How the Process Manager Creates Processes

The information in this section about the Finder information supplements the

description in the Segment Loader.

When a user first opens your application, the Process Manager creates a

partition for it. A partition is a contiguous block of memory that the

Process Manager allocates for the application's use. The partition is

divided into specific areas: application heap, A5 world, and stack. The

application heap contains the application's 'CODE' segment 1, data structures,

resources, and other code segments as needed. The A5 world refers to the

QuickDraw globals, application global variables, and its jump table, all of

which are accessed through the A5 register. The application jump table

contains one entry for every externally referenced routine in every code

segment of your application. The application stack is used to store temporary

variables. See Memory Manager for illustrations of these areas of your

application's partition. When you create an application, you specify in the

'SIZE' resource how much memory you want the

Process Manager to allocate for your application's partition. You specify

two values: the preferred amount of memory to allocate, and the minimum

amount of memory to allocate. When a user opens your application from the

Finder, the Process Manager first attempts to allocate a partition of the

preferred size. If your application cannot be launched in the preferred amount

of memory, the Finder displays a dialog box giving the user the option of

opening the application using less than the preferred size. The Finder will not

launch your application if the minimum amount of memory specified for your

application is not available.

After the Process Manager creates a partition for your application, the

Process Manager loads your code into memory and sets up the stack, heap,

and A5 world ( including the jump table) for your application. If the user

selected one or more files to open or print, the Finder sets up information

your application can use to determine which files to open or print.

The Process Manager assigns the application a process serial number,

records its context, and returns control to the launching application (usually

the Finder). The Process Manager transfers control to the new application

after the launching application makes a subsequent call to WaitNextEvent or

The next section describes how your application can allow other applications

to receive CPU time and how the Process Manager schedules CPU time

among processes.