About The Control Panel
All versions of the Macintosh Operating System previous to system software
speaker volume, date and time, and desktop pattern. With the release of System
file version 4.1, documented in Volume V, the Control Panel became extensible by the addition of control panel files (of file type 'cdev') to the
System Folder.
In System 7.0, the Control Panel, as a discrete desk accessory, has been eliminated. Instead, the Finder can now open each file of file type 'cdev'. Each
control panel file is now displayed as an independent dialog box rather than as a
This and related topics describes how to write a control panel file that is
compatible with both the earlier Control Panel and version 7.0 , and how to write an extension for the Monitors control panel file.
The dialog box defined by a file of file type 'cdev' is referred to as
control panel (as opposed to the Control Panel), and the file itself is referred to as a control panel file.
Only the manufacturer of a video device should write an extension to the
Monitors control panel for that device. Therefore, if you are not developing a
video card for the Macintosh computer, you do not need the information given
here on the Monitors control panel.
control panel devices, or cdevs, that control the status of system-wide
configuration p references. There are a number of cdevs that can come with the
standard System Software, and it is expandable.
When you open the Control Panel by selecting it from the menu, it looks into the System Folder, pulls out the control panel devices and puts their
names and icons into a list along the left margin of the
Control Panel window. If you've got more items than can be displayed in the
list all at once, you can scroll down until you either find the icon you want or
run out of items. The General cdev always tops the list and the settings
available through General fill the remainder of the Control Panel window.
Cdevs are standalone items, with their own standard structure and interface.
Control Panel window, finding out if a particular machine is capable of using
a given cdev, responding to user requests for one cdev or an other, paying
attention to what users do with a chosen cdev, drawing a cdev's dialog items,
telling the cdev when it's time to perform a particular function, and both
displaying errors and drawing active and inactive rectangles in the cdev's part
of the window if the cdev wants.
The cdev takes care of giving the Control Panel the standard resources it needs to execute the cdev's instructions, drawing and responding to actions by
the user, handling errors, starting up and shutting down when told to do so by
the Control Panel, handling updates, responding to user activity and, ultimately, performing the actions it's designed to perform.