What is Daemon?
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The word "daemon" actually comes from the Greek language, meaning an "inner or attendant spirit" (Oxford American Dictionary). This is a fitting name, as a computer daemon is a constantly running program that triggers actions when it receives certain input.
For example, a printer daemon spools information to a printer when a user decides to print a document. A daemon running on a mail server routes incoming mail to the appropriate mailboxes. Web servers use an "HTTPD" daemon that sends data to users when they access Web pages. While daemons were first used by the Unix operating system, they have also been incorporated into Mac OS X, which is Unix-based.
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What is Dashboard?
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Dashboard is a user-interface feature Apple introduced with the release of Mac OS X 10.4 Tiger. It allows access to all kinds of "widgets" that show the time, weather, stock prices, phone numbers, and other useful data. With the Tiger operating system, Apple included widgets that do all these things, plus a calculator, language translator, dictionary, address book, calendar, unit converter, and iTunes controller. Besides the bundled widgets, there are also hundreds of other widgets available from third parties that allow users to play games, check traffic conditions, and view sports scores, just to name a few.
The dashboard of widgets is accessed by clicking the Dashboard application icon, or by simply pressing a keyboard shortcut (F12 by default). Clicking a plus "+" icon in the lower-left hand corner of the screen provides the user with a list of all installed widgets. Clicking the widgets or dragging them onto the desktop makes them active. They can be individually closed by clicking the close box, just like other open windows. Pressing the keyboard shortcut (F12) makes them instantly disappear, removing them from view until the user needs them again.
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What is Database?
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This is a data structure used to store organized information. A database is typically made up of many linked tables of rows and columns. For example, a company might use a database to store information about their products, their employees, and financial information. Databases are now also used in nearly all e-commerce sites to store product inventory and customer information. Database software, such as Microsoft Access, FileMaker Pro, and MySQL is designed to help companies and individuals organize large amounts of information in a way where the data can be easily searched, sorted, and updated.
While the first databases were relatively "flat" (limited to simple rows and columns), today's relational databases allow users to access, update, and search information based on the relationship of data in one database to another. Certain databases even let users store data such as sound clips, pictures, and videos.
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What is DBMS?
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Stands for "Database Management System." In short, a DBMS is a database program. Technically speaking, it is a software system that uses a standard method of cataloging, retrieving, and running queries on data. The DBMS manages incoming data, organizes it, and provides ways for the data to be modified or extracted by users or other programs.
Some DBMS examples include MySQL, PostgreSQL, Microsoft Access, SQL Server, FileMaker, Oracle, RDBMS, dBASE, Clipper, and FoxPro. Since there are so many database management systems available, it is important for there to be a way for them to communicate with each other. For this reason, most database software comes with an Open Database Connectivity (ODBC) driver that allows the database to integrate with other databases. For example, common SQL statements such as SELECT and INSERT are translated from a program's proprietary syntax into a syntax other databases can understand.
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What is DDR?
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Stands for "Double Data Rate." It is an advanced version of SDRAM, a type of computer memory. DDR-SDRAM, sometimes called "SDRAM II," can transfer data twice as fast as regular SDRAM chips. This is because DDR memory can send and receive signals twice per clock cycle. The efficient operation of DDR-SDRAM makes the memory great for notebook computers since it uses up less power.
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What is DDR2?
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Stands for "Double Data Rate 2." DDR2 RAM is an improved version of DDR memory that is faster and more efficient. Like standard DDR memory, DDR2 memory can send data on both the rising and falling edges of the processor's clock cycles. This nearly doubles the amount of work the RAM can do in a given amount of time. DDR and DDR2 are also both types of SDRAM, which allows them to run faster than conventional memory.
While DDR and DDR2 have many similarities, DDR2 RAM uses a different design than DDR memory. The improved design allows DDR2 RAM to run faster than standard DDR memory. The modified design also gives the RAM more bandwidth, which means more data can be passed through the RAM chip at one time. This increases the efficiency of the memory. Since DDR2 runs more efficiently than standard DDR memory, it actually uses less power than DDR memory, even though it runs faster. The only downside of DDR2 memory is that it is not compatible with standard DDR slots. So make sure your computer supports DDR2 RAM before upgrading your memory.
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What is Dead Link?
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A dead link is a link on the world wide web that points to a webpage or server that is permanently unavailable. Dead links are commonplace on the Internet, but they are considered to be unprofessional.
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What is Debug?
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Computer programmers, like everybody else, are not perfect. This means the programs they write sometimes have small errors, called "bugs," in them. These bugs can be minor, such as not recognizing user input, or more serious, such as a memory leak that crashes the program. Before releasing their software to the public, programmers "debug" their programs, eliminating as many errors as possible. This debugging process often takes a long time, as fixing some errors may introduce others. Debugging your windshield at a gas station is much easier than debugging a computer program.
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What is Debugger?
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Even the most experienced software programmers usually don't get it right on their first try. Certain errors, often called bugs, can occur in programs, causing them to not function as the programmer expected. Sometimes these errors are easy to fix, while some bugs are very difficult to trace. This is especially true for large programs that consist of several thousand lines of code.
Fortunately, there are programs called debuggers that help software developers find and eliminate bugs while they are writing programs. A debugger tells the programmer what types of errors it finds and often marks the exact lines of code where the bugs are found. Debuggers also allow programmers to run a program step by step so that they can determine exactly when and why a program crashes. Advanced debuggers provide detailed information about threads and memory being used by the program during each step of execution. You could say a powerful debugger program is like OFF! with 100% deet.
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What is Default?
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This term is used to describe a preset value for some option in a computer program. It is the value used when a setting has not been specified by the user. For example, the default font setting in Netscape Communicator is "Times." If you don't go to the Netscape preferences and change it to something else, the "Times" font will be used -- by default. Typically, default settings are set to what most people would choose anyway, so there's often no reason to change them. However, if you're one of those people who has to customize everything that you possibly can, then you can go ahead and change all the default settings you want.
"Default" can also be used as a verb. If a custom setting won't work for some reason, the program will "default" to the default setting. For example, say you're working on computer that is on a network and you print something when there is no printer specified. If you're lucky and don't get some nasty error message, the print job will default to the default printer and your work will be printed.
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What is Defragment?
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Defragmenting your hard disk is a great way to boost the performance of your computer. Though the term "defragment" sounds a little abrasive, it is actually a simple and helpful process. After all, a defragmented hard disk is a happy hard disk.
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What is Degauss?
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Ever wonder what that "degauss" button on your monitor does besides make a buzzing noise and cause the screen to go crazy for a second? Though that's its main purpose, the degauss button has another useful feature. To understand it, you'll first need to know that the earth has natural magnetic fields. The magnetic charges from these fields can build up inside your monitor, causing a loss of color accuracy. Degaussing scares the bad magnetism out of the monitor and fills it with good karma. If your monitor doesn't have a degauss button, fear not -- many new monitors automatically degauss themselves. If you have a flat-panel display, there is no degauss button because magnetism doesn't build up in flat screen displays.
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What is Delete?
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Delete is computer terminology for remove or erase. You can delete text from a document of delete entire files or folders from your hard drive. When typing a document, you can remove characters behind the cursor by pressing the delete key. If you want to remove characters in front of the cursor, you can press the smaller delete key near the home and end buttons on the keyboard. You can also remove entire sections of text by selecting the text you wish to delete and pressing either delete button on the keyboard.
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What is Desktop?
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Your computer's desktop is much like a physical desktop. You probably keep a number of commonly used items on your desk such as pens, papers, folders, and other items. Your computer's desktop serves the same purpose -- to give you easy access to items on your hard drive. It is common to store frequently used files, folders, and programs on your desktop. This allows you to access the items quickly instead of digging through the directories on your hard drive each time you want to open them.
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What is Desktop Publishing?
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When documents and images are printed, they are "published." Before computers became commonplace, the publishing process required large print presses that copied and duplicated pages. In order to print images and words on the same page, the text and graphics would have to printed separately, cut out, placed on a single sheet, taped in place, then copied and printed. Fortunately, computers with graphical user interfaces have enabled desktop publishing, which allows this process to be done electronically.
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What is DHCP?
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Stands for "Dynamic Host Configuration Protocol." A network server uses this protocol to dynamically assign IP addresses to networked computers. The DHCP server waits for a computer to connect to it, then assigns it an IP address from a master list stored on the server. DHCP helps in setting up large networks, since IP addresses don't have to be manually assigned to each computer on the network. Because of the slick automation involved with DHCP, it is the most commonly used networking protocol.
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What is DHTML?
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Dynamic HTML or DHTML designates a technique of creating interactive web sites by using a combination of the static markup language HTML, a client-side scripting language (such as JavaScript) and the style definition language Cascading Style Sheets.
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What is Dialog Box?
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As the name implies, a dialog box serves to initiate a dialog with the user. It is a window that pops up on the screen with options that the user can select. After the selections have been made, the user can typically click "OK" to enter the changes or "Cancel" to discard the selections. It is customary for menu options that include an ellipsis at the end, such as "Preferences..." or "Save As...", to open a dialog box when selected.
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What is Digital?
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Direct3D is an application program interface (API) developed by Microsoft that provides a set of commands and functions for manipulating 3D objects. By using Direct3D commands, software developers can take advantage of many prewritten functions. This allows programmers to write significantly less code than if they had to write all the functions from scratch. Direct3D makes it relatively easy to manage three-dimensional objects, including lighting and shadows as well.
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What is Digitize?
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When you "digitize" something, you convert it from analog to digital. For example, if you import a VHS tape from a VCR into your computer, you might use an analog-to-digital converter (DAC) to convert the analog signal to a digital stream of data. This is because computers are digital devices and can only read digital data.
Digital files are created by taking samples of analog data, typically at the rate of several thousand per second. For example, a sampling rate of 44.1 kHz, which is what standard audio CDs use, indicates that the audio is being sampled 44,100 times every second. Therefore, the higher the sampling rate, the better the quality of the digitized file.
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What is DIMM?
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Stands for "Dual In-Line Memory Module." It is a type of computer memory. A DIMM is a small circuit board that holds memory chips. It uses a 64-bit bus to the memory, whereas a single in-line memory module (SIMM) only has a 32-bit path. This allows DIMMs to transfer more data at once. Because DIMMs have faster data transfer capabilities than SIMMs, they have pretty much replaced SIMMs.
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What is Direct3D?
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Direct3D is an application program interface (API) developed by Microsoft that provides a set of commands and functions for manipulating 3D objects. By using Direct3D commands, software developers can take advantage of many prewritten functions. This allows programmers to write significantly less code than if they had to write all the functions from scratch. Direct3D makes it relatively easy to manage three-dimensional objects, including lighting and shadows as well.
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What is Directory?
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In computing, a directory, catalog, or folder, is an entity in a file system which contains a group of files and other directories. A typical file system contains thousands of files, and directories help organize them by keeping related files together. A directory contained inside another directory is called a subdirectory of that directory. Together, the directories form a hierarchy, or tree structure.
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What is DirectX?
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DirectX is a set of standard commands and functions that software developers can use when creating their programs. While any Windows-based software program can include DirectX commands, they are usually used in video games. For example, developers may use DirectX for controlling video playback, sound effects, and peripheral input (such as a keyboard, mouse, or joystick). By incorporating DirectX functions into a computer game, programmers can use predefined commands to manage the video and sound of their game, as well as user input. This makes it easier for programmers to develop video games and also helps the games look more uniform, since DirectX games use many of the same commands.
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What is DLL?
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Stands for "Dynamic Link Library." A DLL (.dll) file contains a library of functions and other information that can be accessed by a Windows program. When a program is launched, links to the necessary .dll files are created. If a static link is created, the .dll files will be in use as long as the program is active. If a dynamic link is created, the .dll files will only be used when needed. Dynamic links help programs use resources, such as memory and hard drive space, more efficiently.
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What is DNS?
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The Domain Name Server (System) or DNS is a system that stores information about host names and domain names in a kind of distributed database on networks, such as the Internet. Most importantly, it provides an IP address for each host name, and lists the mail exchange servers accepting e-mail for each domain.
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What is DNS Record?
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DNS records are stored in zone files and are used for translating domain names to IP addresses. They also contain other data, including the domain name's name server and mail server information. If there are domain name aliases, such as the commonly used "www" preceding the domain name, these will also be listed in the DNS record.
A typical DNS record may look something like this:
; Nameservers
;
IN NS ns1.4servers.com. ; 123.456.789.01
IN NS ns2.4servers.com. ; 123.456.789.02
;
; Domain Mail Handlers
;
yourdomain.com. IN MX 0 mail
yourdomain.com. IN MX 10 mail
;
;
; hosts in order
;
yourdomain. IN A Your.IP.XXX
www IN A Your.IP.XXX
smtp IN CNAME www
pop IN CNAME www
ftp IN CNAME www
mail IN A Your.IP.XXX
;
; end
Since DNS records are made up entirely of text, they are easy to modify when needed. However, one small typo could redirect a domain name to the wrong Web server or prevent it from showing up at all. This is why it is important to enter DNS information accurately and double-check your changes entry before saving the zone file.
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What is Domain Name?
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A domain name is the unique name of a computer on the Internet that distinguishes it from the other systems on the network.
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What is Dongle?
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This funny-sounding computer term has two widely different definitions that are completely unrelated:
1. A security key. This is a little hardware device that plugs into the serial or USB port of a computer. Its purpose is to ensure that only authorized users can use certain software applications. If you have never seen a dongle, don't be surprised. They are only used with expensive, high-end software programs that most people have never heard of, much less use. When a program that comes with a dongle runs, it checks the dongle for verification as it is loading. If it doesn't find the dongle, the computer explodes. Well, not really -- usually the program just quits. If more than one application requires a dongle, multiple dongles using the same port can be daisy-chained together. Basically, if you ever find yourself daisy-chaining multiple dongles together, you must be doing pretty well in life.
2. A laptop Ethernet card adapter. This is a little connector that attaches to a PC card in a laptop on one end, and to an Ethernet cable on the other end. Since most PC (or PCMCIA) network interface cards are too small to connect directly to a standard RJ-45 Ethernet cable, they need this little adapter that connects the card to the cable. (3Com cards that use an "X-Jack" connector do not need a dongle.) As far as why the name dongle is used, I have no idea.
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What is Doorway Page?
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Doorway pages are web pages that are created to rank high in search engines for particular phrases with purpose to seduce or hoax you to watch another page. They are also known as bridge pages, portal pages, zebra pages, jump pages, gateway pages, entry pages and by other names.
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What is Dot Pitch?
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This is the measurement used to determine how sharp the display of a CRT (Cathode Ray Tube) monitor is. It is measured in millimeters and the smaller the number, the finer the picture. Most CRT monitors will have a dot pitch between .25 and .28. However, some large presentation monitors have dot pitches from .30 to .50 (which would make for really fuzzy images on a standard 17" desktop monitor). The difference between a "dot" (as in dot pitch) and a pixel is that a pixel is mapped onto the dots on the screen. When the monitor is set to lower resolutions, one pixel encompasses multiple dots. So pixels are typically larger than the "dots" on the actual screen.
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What is Double Click?
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Double clicking involves clicking your mouse button quickly two times. To perform a double click, and not just two clicks, the mouse button must be pressed twice within a very short time, typically about half a second. Most operating systems allow you to lengthen or shorten the maximum time allowed for a double click, using the Mouse Control Panel or System Preference.
A double click is recognized by your computer as a specific command, just like pressing a key on your keyboard. Double clicking is used to to perform a variety of actions, such as opening a program, opening a folder, or selecting a word of text. In order to double click an object, just move the cursor over the item and press the left mouse button quickly two times.
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What is Download?
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The process of retrieving information from any computer to your computer is called downloading.
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What is Drag?
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You can use your mouse to drag icons and other objects on your computer screen. Dragging icons from your desktop or an open window to another folder will move the objects to the new folder. You can also drag icons to the Trash (Mac) or the Recycle Bin (Windows) if you want to delete tehm. Some word processing programs allow you to select text and drag the selected text to another place in the document. To select the text, you may have to "drag" the mouse over the text you want to select.
Dragging is an important technique for using today's graphical user interfaces (GUIs). In fact, there are many other things you can drag besides icons. For example, you can drag the top of windows to reposition them, you can drag the scroll bar in open documents or Web pages to scroll through them, and you can drag messages to different folders in your mail program. Other programs, such as video games and image-editing programs use dragging to reposition items on the screen.
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What is Driver?
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This term usually refers to the person behind the wheel of a moving car. In the computer world, however, a driver is a small file that helps the computer communicates with a certain hardware device. It contains information the computer needs to recognize and control the device. In Windows-based PCs, a driver is often packaged as a dynamic link library, or .dll file. In Macs, most hardware devices don't need drivers, but the ones that do usually come with a software driver in the form of a system extension, or .kext file.
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What is DRM?
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Stands for "Digital Rights Management." DRM refers to a collection of systems used to protect the copyrights of electronic media. These include digital music and movies, as well as other data that is stored and transferred digitally. For example, the Apple iTunes Music Store uses a DRM system to limit the number of computers that songs can be played on. Each audio file downloaded from the iTunes music store includes information about the owner of the file and how many times the file has been transferred. The protected files will not play on computers that have not been authorized to play the music.
Digital Rights Management is important to publishers of electronic media since it helps ensure they will receive the appropriate revenue for their products. By controlling the trading, protection, monitoring, and tracking of digital media, DRM helps publishers limit the illegal propagation of copyrighted works. This can be accomplished by using digital watermarks or proprietary file encryption on the media they distribute. Whatever method publishers choose to employ, DRM helps them make sure that their digital content is only used by those who have paid for it.
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What is DSL?
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Stands for "Digital Subscriber Line." It is medium for transferring data over regular phone lines and can be used to connect to the Internet. However, like a cable modem, a DSL circuit is much faster than a regular phone connection, even though the wires it uses are copper like a typical phone line.
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What is DTD?
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Stands for "Document Type Definition." A DTD defines the tags and attributes used in an XML or HTML document. Any elements defined in a DTD can be used in these documents, along with the predefined tags and attributes that are part of each markup language. The following is an example of a DTD used for defining an automobile:
]>
The above DTD first defines the header of the item as "Car Details." Then it provides elements to define the make and model of the automobile. The "#PCDATA" data type means it can be any text value). The "ATTLIST" tag on the next line provides options for a specific element. In this case, it states that the model can have either two or four doors. The DTD then provides elements for the year and engine type of the car, followed by a choice of either a manual or automatic transmission for the engine.
The above example is a basic DTD that only uses a few data types. Document type definitions used for large XML databases can be thousands of lines long and can include many other data types. Fortunately, DTDs can be easily modified in a text editor whenever changes need to be made.
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What is DV?
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Stands for "Digital Video." Unlike traditional analog video, which is captured frame by frame on a tape, digital video is recorded digitally, as ones and zeros. Since it is stored in a digital format, digital video can be recognized and edited by a computer, which is also a digital device.
DV camcorders, including Mini DV and HDV, record digital video and therefore can export the footage to a computer using a Firewire (IEEE 1394) cable. Analog camcorders such as SVHS and Hi-8 devices must be run through a analog to digital converter (DAC) in order to be transferred to a computer.
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What is DVD?
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Stands for "Digital Versatile Disc." It can also stand for "Digital Video Disc," but with the mulitple uses of DVDs, the term "Digital Versatile Disc" is more correct. Yep, the technology naming people just love to confuse us. A DVD is a high-capacity optical disc that looks like a CD, but can store much more information. While a CD can store 650 to 700 MB of data, a single-layer, single-sided DVD can store 4.7 GB of data. This enables massive computer applications and full-length movies to be stored on a single DVD.
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What is DVD+R?
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Stands for "Digital Versatile Disc Recordable." DVD+R discs look the same as regular DVDs, but can be used to record data. Single-sided, single-layer DVD+R discs can store 4.7GB of data, while double-layer discs can store 8.5GB and double-sided DVD-Rs can store 9.4GB. The DVD+R format is not quite as common as the DVD-R format, but is still supported by most current DVD players and DVD-ROM drives. Drives that can read both DVD+R and DVD-R discs are often referred to as DVD±R drives.
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What is DVD+RW?
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Stands for "Digital Versatile Disk Rewritable." A DVD+RW is like a DVD+R, but can be erased and rewritten. DVD+RWs must be completely erased in order for new data to be added. DVD+RW discs can hold 4.7GB of data and do not come in double-sided or double-layer versions like DVD+Rs do. Still, 4.7GB of data is a lot of storage space. Combined with their ability to be re-recorded, DVD+RWs are a great choice for making frequent backups of your data. To record data onto a DVD+RW disc, you'll need a DVD burner that supports the DVD+RW format.
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What is DVD-R?
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Stands for "Digital Versatile Disc Recordable." A DVD-R looks the same as a regular DVD, but like a CD-R, it can be used to record data. Once a DVD-R has been "burned," or written to, it cannot be written to again. A basic single-sided, single-layer DVD-R disc can store 4.7GB of data. Double-layer discs can store 8.5GB, while double-sided DVD-Rs can store 9.4GB.
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What is DVD-RAM?
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Stands for "Digital Versatile Disc Random Access Memory." DVD-RAMs are writable DVDs. The discs can also be erased and rewritten like the DVD-RW and DVD+RW formats. However, DVD-RAM discs work only when placed in an enclosing cartridge, meaning they won't fit in most standard DVD players or DVD-ROM drives. The first DVD-RAM media could hold 2.6GB on a single-sided disc, but newer double-sided discs can store up to 9.4GB.
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What is DVD-RW?
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Stands for "Digital Versatile Disk Rewritable." A DVD-RW is like a DVD-R but can be erased and written to again. Like CD-RWs, DVD-RWs must be erased in order for new data to be added. DVD-RWs can hold 4.7GB of data and do not come in double-layered or double-sided versions like DVD-Rs do. Because of their large capacity and ability to be used mulitple times, DVD-RW discs are a great solution for frequent backups. To record data onto a DVD-RW disc, you'll need a DVD burner that supports the DVD-RW format.
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What is DVI?
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Stands for "Digital Video Interface." DVI is a video connection standard created by the Digital Display Working Group (DDWG). Most DVI ports support both analog and digital displays. If the display is analog, the DVI connection converts the digital signal to an analog signal. If the display is digital, no conversion is necessary.
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What is DVR?
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Stands for "Digital Video Recorder." A DVR is basically a VCR that uses a hard drive instead of video tapes. It can be used to record, save, and play back television programs. Unlike a VCR, however, a DVR can also pause live TV by recording the current show in real time. The user can choose to fast forward (often during commercials) to return to live television.
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What is Dynamic Page?
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Information on web pages which changes or is changed automatically. Sometimes it's possible to spot this technique by looking at a page's file extension.
Search engines will currently index dynamic content in a similar fashion to static content.
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