D

daisy chaining

The process of connecting one peripheral or network device to another device, linking them so that they can share data. This is often done with Ethernet networking hubs to extend the size of an Ethernet network. It’s also how multiple FireWire and SCSI devices are connected to a single Macintosh computer so that they can all be accessed by that computer.

Darwin

A joint project between the Open Source community and Apple. The primary objective of the Darwin project is to build an industrial-strength UNIX-based operating system core that provides greater stability and performance compared to the existing iterations of the Mac OS to date.

dead keys

The keys that generate accented characters when typed in combination with the Option key and in proper sequence. For example, typing Option-E followed by O generates on a U.S. keyboard. The Key Caps program highlights the dead keys when you press Option.

default browser

The Web browser application that opens when you click a link to a Web page in Sherlock’s list of search results, open an Internet location file, or otherwise don’t specify a particular browser application.

default button

The one button that pulsates in an Aqua dialog or alert box; in a Classic dialog or alert box, the default button has a heavy border. In either case it represents the action you’ll most often want to take. If the most common action is dangerous, a button representing a safer action may be the default button. Usually, pressing Return or Enter has the same effect as clicking the default button.

Desktop database

Invisible files used by the Finder to associate Classic applications and their documents. Mac OS X keeps the Desktop database hidden because you don’t use it directly. You can use the Classic pane of System Preferences to rebuild the Desktop database.

device A

piece of hardware attached to a computer, either internally or externally. Some examples include keyboards, scanners, and drives.

device driver

Software that controls a device, such as a printer or scanner. The driver contains data that the OS requires to fully utilize the device.

DHCP (Dynamic Host Configuration Protocol)

A networking service in which a host device dynamically assigns TCP/IP addresses to client computers to grant them access to the network.

dialog

A window that displays options you can set or select. A dialog typically has a button for accepting the changes and another button for canceling the changes. Both buttons close the dialog.

digital signature

Functions as a handwritten signature, identifying the person who vouches for the accuracy and authenticity of the signed document.

DIMM

A dual in-line memory module is a small circuit board containing memory chips.

directory

Another name for folder.

Directory Services

Directory Services provide a consolidated user list that can be shared via multiple network services or servers for authentication. Directory Services do not provide the user list data itself but rather describe how they are set up and enable the communication of the data.

disclosure triangle

A displayed control that regulates how much detail you see in a window. When the window is displaying minimal detail, clicking a disclosure triangle reveals additional detail and may automatically enlarge the window to accommodate it. Clicking the same triangle again hides detail and may automatically shrink the window to fit.

disk cache

Improves system performance by storing recently used information from disk in a dedicated part of memory. Accessing information in memory is much faster than accessing information on disk.

disk image

A file that, when mounted using Disk Copy or a similar utility, appears on the Desktop as if it were a removable disk.

display mirroring

See video mirroring

DNS (Domain Name System)

A service that resolves domain names to IP addresses, and vice versa.

DogCow

Also known as Clarus, it is the official mascot of Mac enthusiasts. It looks vaguely like a dog (or a cow, thus the name) and is pictured in the Page Setup Options dialog of Classic applications.

domain name

The part of a URL that identifies the owner of an Internet location. A domain name has the form companyname.com, organizationname.net, schoolname.edu, militaryunitname.mil, governmentagencyname.gov, and so forth.

double-click speed

The rate at which you have to click so that Mac OS X perceives two clicks in a row as a single event.

download

The process of receiving software or other computer files from another computer, over the Internet or a local network.

dpi (dots per inch)

A measure of how fine or coarse the dots are that make up a printed image. More dots per inch means smaller dots, and smaller dots mean finer (less coarse) printing.

drag

To move the mouse while holding down the mouse button.

drag-and-drop editing

To copy or move selected text, graphics, and other material by dragging it to another place in the same window, a different window, or on the desktop. Some applications do not support drag-and-drop editing.

drag-and-drop open

To drag a document to a compatible application in the Finder, thereby highlighting the application, and then releasing the mouse button, causing the application to open the document.

drop box

A shared folder located inside a user’s Public folder in which other users may place items (when peer-to-peer file sharing is enabled), but only the folder’s owner can see them.

DSL (Digital Subscriber Line)

An add-on for standard telephone service that enables you to maintain a constant, high-speed Internet connection over a standard telephone line.

duplex

A method of printing on both sides of the page that does not need a person there to flip the pages.

dynamic IP address

See DHCP

dynamic RAM allocation

An operating system technology that allows the operating system to respond to an application’s request for more or less memory as needed.