Panasonic FP-D250 User Manual page 580

Digital signal A signal with only two values, normally 0 and 1, during transmission,
unlike an analog signal whose values constantly vary.
Digitize To convert an image or other data into a digital representation that may be
processed electronically. You digitize a photograph when you scan it to copy.
Direct attachment The IBM term for linking a device or LAN directly to a host computer
through an appropriate Control Unit, like a cluster controller.
Disk Duplexing A method of fail safe protection, occasionally used on file servers
on local area networks. Disk duplexing involves copying data onto two disks
simultaneously, each through a separate disk channel. The idea is, if one channel is
faulty, the other will continue to operate normally.
Disk Mirroring A fault tolerant technique that writes data simultaneously to two
hard disk drives using the same hard disk controller. The disks operate in tandem,
constantly storing and updating the same files. Mirroring alone does not ensure
data protection. If both disks fail at the same time, you will still lose data.
Disk server A device equipped with disks and a program permitting users to create
and store files on those disks. Each user has access to their own section of disk on
the disk server. The aim is to give users access to disk space that they would not
normally have on their PC. The disk server is linked to the PCs via a LAN. The next
level of sophistication would be a file server.
Distributed computing The trend away from having big, centralized computers
such as mini-computers and mainframes to bring processing power to the desktop.
Often confused with distributed processing.
Distributed processing An approach that allows one application program to execute
on multiple computers linked together by a network. The networked computers share
the work between them.
Dithering Simulating gray tones by altering the size, arrangement or shape of
background dots.
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