Process Management
About Process Management Information on sharing resources
accessories, and allows multiple applications to share the CPU and other
resources. Applications share the available memory and access to the CPU.
Several applications can be open (loaded into memory) at once, but only one
uses the CPU at any one time.
open application or, in some cases, an open desk accessory. (Desk accessories
that are opened in the context of an application are not considered processes.)
In version 7.0, the number of processes is limited only by available memory.
example, the current state of the process, the address and size of its partition,
its type, its creator, a copy of its low-memory globals, information about its
'SIZE' resource, and a process serial number. This process information is
process serial number to identify each process. A process serial number
identifies a particular instance of an application; this number is unique during
a single boot of the local machine.
The foreground process is the one currently interacting with the user; it appears to the user as the active application. The foreground process displays
its menu bar, and its windows are in front of the windows of all other
applications.
A background process is a process that is not currently interacting with the
user. At any given time a process is either in the foreground or the
background; a process can switch between the two states at well- defined times.
The foreground process has first priority for accessing the CPU. Other
processes can access the CPU only when the foreground process yields time to
them. There is only one foreground process at any one time. However, multiple
processes can exist in the background.
An application that is in the background can get CPU time but can not interact
with the user while it is in the background. (However, the user can choose to
bring the application to the foreground-for example, by clicking in one of the
application's windows.) Any application that has the canBackground flag set in
its 'SIZE' resource is eligible to obtain access to the CPU when it is in the
background.
Applications can be designed without a user interface. A background-only
application is an application that does not have a user interface. A
background-only application does not call the InitWindows routine and is
identified by having the onlyBackground flag set in its 'SIZE' resource.
Background-only applications do not display windows or a menu bar and are not
listed in the Application menu. Background-only applications and applications
that can run in the background should be designed to relinquish the CPU often
enough so that the foreground process can perform its work and respond to the
user.
Once an application is executing, in either the foreground or the background,
the CPU is available only to that application. The application can be
interrupted only by hardware interrupts, which are transparent to the
scheduling of the application. However, to give processing time to background
applications and to allow the user to interact with the foreground application
or switch to another application, you must periodically relinquish the CPU
provide greater support for multitasking.) Use these Event Manager functions to let the user interact with your application and also with other
applications.