Direct-Access Storage Device
<hardware> (DASD) IBM mainframe terminology for a disk drive, in contrast
with a tape drive which is a sequential access device.
Diophantine equation « DIP « diplex «
Direct-Access Storage Device » Direct Client to
Client Protocol » Direct Connection » directed
Direct Client to Client Protocol
<networking> (DCC) An IRC protocol created to allow users to chat
privately and to send and receive files directly instead of having to go thorugh
the IRC servers. DCC protects users from being monitored by IRC Server operators
that have enabled conversation logging. It also allows much more efficient use
of available bandwidth as the data does not need to be broadcast all over the
world just to reach a specific user.
The available DCC commands include DCC CHAT (direct user to user chat), DCC SEND
(direct user to user file send) and DCC GET (file acknowledgement from a
DIP « diplex « Direct-Access Storage Device «
Direct Client to Client Protocol » Direct
Connection » directed acyclic graph » directed graph
A re-seller of Internet connections to the PIPEX backbone.
diplex « Direct-Access Storage Device « Direct
Client to Client Protocol « Direct Connection
» directed acyclic graph » directed graph » Directed
directed acyclic graph
(DAG) A directed graph containing no cycles. This means that if there is a route
from node A to node B then there is no way back.
Direct-Access Storage Device « Direct Client to
Client Protocol « Direct Connection « directed
» directed graph » Directed Oc » directed set
(digraph) A graph with one-way edges.
See also directed acyclic graph.
Direct Client to Client Protocol « Direct Connection
« directed acyclic graph « directed graph »
Directed Oc » directed set » Direct Inward Dialing
<language> (Doc) A language related to Oc.
["Programming Language Doc and Its Self-Description, or 'X=X Is Considered
Harmful'", M. Hirata, Proc 3rd Conf Japan Soc Soft Sci Tech, pp. 69-72, 1986].
Direct Connection « directed acyclic graph «
directed graph « Directed Oc » directed set »
Direct Inward Dialing » directional coupler
<theory> A set X is directed under some relation, <= (less than or
equal), if it is non-empty and if for any two elements x and y there exists an
element z such that x <= z and y <= z. I.e. all pairs have an upper bound.
directed acyclic graph « directed graph « Directed
directed set » Direct Inward Dialing »
directional coupler » Directly Executable Test
Direct Inward Dialing
<communications> (DID) A service offered by telephone companies which
allows the last 3 or 4 digits of a phone number to be transmitted to the
For example, a company could have 10 incoming lines, all with the number 234
000. If a caller dials 234 697, the call is sent to 234 000 (the company's
exchange), and the digits 697 are transmitted. The company's exchange then
routes the call to extension 697. This gives the impression of 1000 direct dial
lines, whereas in fact there are only 10. Obviously, only 10 at a time can be
This system is also used by fax servers. Instead of an exchange at the end of
the 234 000 line, a computer running fax server software and fax modem cards
uses the last three digits to identify the recipient of the fax. This allows
1000 people to have their own individual fax numbers, even though there is only
one 'fax machine'.
Dictionary of PC Hardware and Data Communications Terms.
directed graph « Directed Oc « directed set «
Direct Inward Dialing » directional coupler »
Directly Executable Test Oriented Language » direct
<communications> (tap) A passive device used in cable systems to divide
and combine radio frequency signals. A directional coupler has at least three
ports: line in, line out, and the tap. The signal passes between line in and
line out ports with loss referred to as the insertion loss. A small portion of
the signal power applied to the line in port passes to the tap port. A signal
applied to the tap port is passed to the line in port less the tap attenuation
value. The tap signals are isolated from the line out port to prevent
reflections. A signal applied to the line out port passes to the line in port
and is isolated from the tap port. Some devices provide more than one tap output
Directed Oc « directed set « Direct Inward Dialing «
directional coupler » Directly Executable Test
Oriented Language » direct mapped cache » Direct
Directly Executable Test Oriented Language
<language> (DETOL) A simple language to control a specific type of test
["Improved DETOL Programming Manual for the Series 5500 Automatic Test System",
Pub. 5500-31-0-1, AAI Corporation Sep 1973].
directed set « Direct Inward Dialing « directional
Directly Executable Test Oriented Language »
direct mapped cache » Direct Memory Access »
direct mapped cache
<architecture> A cache where the cache location for a given address is
determined from the middle address bits. If the cache line size is 2^n then the
bottom n address bits correspond to an offset within a cache entry. If the cache
can hold 2^m entries then the next m address bits give the cache location. The
remaining top address bits are stored as a "tag" along with the entry.
In this scheme, there is no choice of which block to flush on a cache miss since
there is only one place for any block to go. This simple scheme has the
disadvantage that if the program alternately accesses different addresses which
map to the same cache location then it will suffer a cache miss on every access
to these locations. This kind of cache conflict is quite likely on a
multi-processor. See also fully associative cache, set associative cache.
Direct Inward Dialing « directional coupler «
Directly Executable Test Oriented Language «
direct mapped cache
» Direct Memory Access » directory » Directory
Direct Memory Access
<architecture> (DMA) A facility of some architectures which allows a
peripheral to read and write memory without intervention by the CPU. DMA is a
limited form of bus mastering.
directional coupler « Directly Executable Test
Oriented Language « direct mapped cache « Direct
» directory » Directory Access Protocol » directory
<file system> A node in a hierarchical file system which contains zero or
more other nodes - generally, files or other directories.
Directly Executable Test Oriented Language « direct
mapped cache « Direct Memory Access « directory
» Directory Access Protocol » directory service »
Directory System Agent
Directory Access Protocol
X.500 protocol used for communication between a Directory User Agent and a
Directory System Agent.
direct mapped cache « Direct Memory Access «
Directory Access Protocol » directory service »
Directory System Agent » Directory User Agent
<database, networking> A structured repository of information on people
and resources within an organisation, facilitating management and communication.
On a LAN or WAN the directory service identifies all aspects of the network
including users, software, hardware, and the various rights and policies
assigned to each. As a result applications can access information without
knowing where a particular resource is physically located, and users interact
oblivious to the network topology and protocols.
To allow heterogeneous networks to share directory information the ITU proposed
a common structure called X.500. However, its complexity and lack of seamless
Internet support led to the development of Lightweight Directory Access Protocol
(LDAP) which has continued to evolve under the aegis of the IETF. Despite its
name LDAP is too closely linked to X.500 to be "lightweight".
LDAP was adopted by several companies such as Netscape Communications
Corporation (Netscape Directory Server) and has become a de facto standard for
directory services. Other LDAP compatible offerings include Novell, Inc.'s
Novell Directory Services (NDS) and Microsoft Corporation's Active Directory.
The Netscape and Novell products are available for Windows NT and Unix
platforms. Novell Directory Services also run on Novell platforms. Microsoft
Corporation's Active Directory is an integral part of Microsoft's Windows 2000
and although it can interface with directory services running on other systems
it is not available for other platforms.
Direct Memory Access « directory « Directory Access
Protocol « directory service » Directory
System Agent » Directory User Agent » DirectX
Directory System Agent
(DSA) The software that provides the X.500 Directory Service for a portion of
the directory information base. Generally, each DSA is responsible for the
directory information for a single organisation or organisational unit.
directory « Directory Access Protocol « directory
Directory System Agent » Directory User Agent »
DirectX » Dirt
Directory User Agent
(DUA) The software that accesses the X.500 Directory Service on behalf of the
directory user. The directory user may be a person or another software element.
Directory Access Protocol « directory service «
Directory System Agent « Directory User Agent
» DirectX » Dirt » dirtball
<programming, hardware> A Microsoft programming interface standard, first
included with Windows 95. DirectX gives (games) programmers a standard way to
gain direct access to enhanced hardware features under Windows 95 instead of
going via the Windows 95 GDI. Some DirectX code runs faster than the equivalent
under MS DOS.
DirectX promises performance improvements for graphics, sound, video, 3D, and
network capabilites of games, but only where both hardware and software support
DirectX 2 introduced the Direct3D interface. Version 5 was current at
1998-02-01. Version 8.1 is included in Windows XP.
Current version: 8.1 (as of 2001-12-31).
directory service « Directory System Agent «
Directory User Agent « DirectX » Dirt »
dirtball » dirty power