PC Hardware

Technical Terms Beginning With D

data bus

A group of parallel conductors (circuit traces) found on the motherboard that is used by the CPU to send and receive data from all the devices in the computer. Also called the external data bus.

Data Communications Equipment (DCE)

The receiver in a telecommunications connection.

default drive

The active drive on the computer. Each drive has its own letter designation. Unless otherwise specified, any commands are performed upon the default drive.


Running a program to organize the files on a hard disk so that the various clusters of data for each file are once again contiguous. This helps to speed up the hard disk.

device driver

A program that extends the operating system to support specific devices.

direct memory access (DMA)

Allows a peripheral device to access the memory of a computer directly, without going through the CPU. This speeds up the transfer of data to or from external devices.


A location where files are grouped together on the disk. In the Microsoft Windows environment and Apple Macintosh operating systems, these are known as folders.

DLC (Data Link Control)

A protocol developed by IBM to connect token-ring-based workstations to IBM mainframe computers. Printer manufacturers have adopted the protocol to connect remote printers to network print servers.


See direct memory access

DOS (disk operating system)

The system used by most early PCs as the operating system software to manage hardware, data, and applications.

DOS prompt

Displays the active drive letter (for instance, C:) and directory. This indicates that the operating system is ready to accept the next command.

DOS Protected Mode Interface (DPMI)

Specification that allows multiple applications to access extended memory at the same time. It has been endorsed by most memory manager producers and application developers. Microsoft Windows uses the DPMI specification.


The ability to transfer a file from a remote computer.

dpi (dots per inch)

Units used to measure the resolution of images on many printers and scanners. Keep in mind that dpi is an exact measurement in laser printers, but often used as an approximation in ink jet printers.

DRAM (dynamic random access memory)

Memory that requires a refresh signal to be sent to it periodically.

Dynamic Data Exchange (DDE)

A data exchange protocol that allows for the automatic updating of a file or open application when the source is modified.