Author Topic: Computer Terms Beginning with "D"  (Read 7277 times)

Offline MysteRy

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Re: Computer Terms Beginning with "D"
« Reply #60 on: March 28, 2014, 03:33:39 PM »
DTD

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:

<!DOCTYPE automobile [
   <!ENTITY header "Car Details">
   <!ELEMENT make (#PCDATA)>
   <!ELEMENT model (#PCDATA)>
   <!ATTLIST model doors (two | four) #required>
   <!ELEMENT year (#PCDATA)>
   <!ELEMENT engine (#PCDATA)>
   <!ATTLIST engine transmission (manual | automatic) #required>
]>

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.

Offline MysteRy

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Re: Computer Terms Beginning with "D"
« Reply #61 on: March 28, 2014, 03:34:22 PM »
Dual-Core

A dual-core processor is a CPU with two processors or "execution cores" in the same integrated circuit. Each processor has its own cache and controller, which enables it to function as efficiently as a single processor. However, because the two processors are linked together, they can perform operations up to twice as fast as a single processor can.

The Intel Core Duo, the AMD X2, and the dual-core PowerPC G5 are all examples of CPUs that use dual-core technologies. These CPUs each combine two processor cores on a single silicon chip. This is different than a "dual processor" configuration, in which two physically separate CPUs work together. However, some high-end machines, such as the PowerPC G5 Quad, use two separate dual-core processors together, providing up to four times the performance of a single processor.

While a dual-core system has twice the processing power of a single-processor machine, it does not always perform twice as fast. This is because the software running on the machine may not be able to take full advantage or both processors. Some operating systems and programs are optimized for multiprocessing, while others are not. Though programs that have been optimized for multiple processors will run especially fast on dual-core systems, most programs will see at least some benefit from multiple processors as well.

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Re: Computer Terms Beginning with "D"
« Reply #62 on: March 28, 2014, 03:34:56 PM »
DV

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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Re: Computer Terms Beginning with "D"
« Reply #63 on: March 28, 2014, 03:35:29 PM »
DVD

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.

The advanced DVD formats are even more amazing. There is a two-layer standard that doubles the single-sided capacity to 8.5 GB. These disks can also be double-sided, ramping up the maximum storage on a single disc to 17 GB. That's 26 times more data than a CD can hold! To be able to read DVDs in your computer you'll need a DVD-ROM drive. Fortunately, DVD players can also read CDs. To play DVD movies on your computer, you'll need to have a graphics card with a DVD-decoder, which most computers now have.

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Re: Computer Terms Beginning with "D"
« Reply #64 on: March 28, 2014, 03:36:05 PM »
DVD+R

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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Re: Computer Terms Beginning with "D"
« Reply #65 on: March 28, 2014, 03:36:36 PM »
DVD+RW

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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Re: Computer Terms Beginning with "D"
« Reply #66 on: March 28, 2014, 03:37:14 PM »
DVD-R

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.

DVD-R is the most common format of writable DVDs (compared to the DVD+R and DVD-RAM formats). Most DVD players and DVD-ROM drives can read DVD-R discs. That means you can use a DVD-R disc to back up several gigabytes of data on your computer or make your own video DVD. The Apple SuperDrive used in many Macintosh computers supports the DVD-R format.

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Re: Computer Terms Beginning with "D"
« Reply #67 on: March 28, 2014, 03:37:47 PM »
DVD-RAM

Example: "DVD-RAM discs can be erased and rewritten over 100,000 times."

DVD-RAM stands for "Digital Versatile Disc - Random Access Memory." It is one of three rewriteable DVD formats, along with DVD+RW and DVD-RW. DVD-RAM discs are available as bare discs, or removable and non-removable cartridge formats. The cartridge formats can only be used with a specific DVD-RAM drive, while bare discs can be used with any DVD drives that recognize the DVD-RAM format. Single-sided DVD-RAM discs support capacities of 4.7GB, while dual-sided DVD-RAM discs support 9.4GB.

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Re: Computer Terms Beginning with "D"
« Reply #68 on: March 28, 2014, 03:38:18 PM »
DVD-RW

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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Re: Computer Terms Beginning with "D"
« Reply #69 on: March 28, 2014, 03:38:51 PM »
DVI

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.

There are three types of DVI connections: 1) DVI-A (for analog), 2) DVI-D (for digital), and 3) DVI-I (integrated, for both analog and digital). The digital video interface supports high bandwidth signals, over 160 MHz, which means it can be used for high resolution displays such as UXGA and HDTV. You may find DVI ports on video cards in computers as well as on high-end televisions.

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Re: Computer Terms Beginning with "D"
« Reply #70 on: March 28, 2014, 03:39:31 PM »
DVR

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.

Most satellite and cable TV companies offer a DVR as an option with their digital television packages. Since cable boxes already provide program listings through some kind of TV guide interface, most DVRs allow users to use the guide to schedule recordings. For example, a user can use the remote to search through the guide's program listings for the current week and select the shows he would like to record.

TiVo, the "brand name" DVR, performs the same functions as a DVR offered directly from a cable company. However, TiVo users can choose to buy the DVR box instead of renting it. Since TiVo is a standalone box, it does not require cable or satellite TV. While TiVo users who buy their own TiVo boxes may avoid the monthly rental fees, they must pay a monthly fee for program listings if they want to schedule recordings.

DVRs conveniently save shows in an list that the user can access at any time. Since the shows are stored on DVR's hard drive, there is no need to rewind or fast forward to play a certain show, like a VCR requires. While DVRs make it even easier to record your favorite shows every week or even every day, it also makes it easier to watch more TV. And an excuse to watch more TV is something most of us don't need.

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Re: Computer Terms Beginning with "D"
« Reply #71 on: March 28, 2014, 03:40:07 PM »
Dynamic Website

Example: "The softball association created a dynamic website that provides current team and player stats."

A dynamic website contains Web pages that are generated dynamically. Each time a user accesses a page within a dynamic site, the HTML is generated in real-time and is sent to the user's Web browser. The content is typically accessed from a database, which is why dynamic websites are often called "database-driven" sites. Most large sites contain dynamic content, while smaller sites may be designed as static websites.