iMac as well as every desktop model of the Macintosh computer, comes standard with an Apple-branded keyboard. Originally a USB keyboard was the standard offering, but Apple changed to a wireless model in 2007. All Apple keyboards include a row of function keys above the row of number keys, commonly referred to as “F” keys. Most third-party keyboards also include a row of “F” keys.
Apple Keyboards - All recent Apple wired keyboard models connect via USB. Three distinct styles of Apple keyboards have been packaged with iMacs since the G4 model in 2002. The first is the white plastic wired model, which contains "F" keys F1 through F15. The second is the aluminum wired keyboard, which also contains the same number of function keys. The third model is the aluminum wireless keyboard that features a truncated design, without a number pad on the right, includes only F1 through F12 "F" keys. As of the date of publication, the wireless model is the default model that is included with every new iMac.
'F' Key Icons -In addition to the standard labeling of the "F" keys -- the key on the far left is labeled F1, the key to its right is labeled F2 and so on -- some Apple "F" keys' functions are indicated by a small icon. These include F2 for screen brightness, F11 for volume up, F12 for volume down and F10 for volume mute, as well as keys F7 through F9 for iTunes commands.
System-Level 'F' Key Shortcuts -'F' keys are smaller than standard keys on Apple keyboards. "F" keys on your Mac are assigned certain tasks by default, but they can also be programmed for specific purposes in both the Mac OS or within applications. To change the system function of an "F" key on your iMac, open "System Preferences" from under the Apple icon in the upper left corner of the screen, click "Keyboard" and then "Keyboard Shortcuts" tab. By double-clicking a specific shortcut, you can reprogram its function.
Application 'F' Key Shortcuts - Mapping is the process of assigning shortcuts to 'F' keys. "F" keys are also used by power users for performing often-repeated tasks within an application, such as Adobe Photoshop or Microsoft Word. So if you're in the Mac OS, hitting F2 increases your display brightness; in Photoshop CS3, it's the shortcut for "cut." As with the "F" keys in the Apple OS, you can program your "F" keys to perform a custom function within certain applications. In Photoshop, pull down the Edit menu and select "Keyboard Shortcuts and Menu" to remap your "F" keys. In Word, from the Tools menu, select "Customize Keyboard." Some, but not all other applications allow you to reprogram your "F" key functions.
Occasional Changes - Apple changes the functions on some "F" keys from time to time, usually when a new version of the OS is released, so, for example, the "F" keys on an iMac running Tiger, OS 10.3, at your workstation and an iMac running Leopard, OS 10.5, at your home have different functions. For example, when the dashboard was introduced in Tiger, the F4 key function was changed to be dedicated to dashboard functions.