Computer Terms Beginning with "D"

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Source : PC.net

DAC

Stands for "Digital-to-Analog Converter" and is often pronounced "dac." Since computers only recognize digital information, the output produced by computers is typically in digital format. However, some output devices only accept analog input, which means a digital-to-analog converter, or DAC, must be used.

The most common use for a DAC is to convert digital audio to an analog signal. This conversion typically takes place in the sound card, which has a built-in DAC. The digital signal, which is basically a stream of ones and zeros, is transformed into an analog signal that might take the form of an electrical charge. This electrical charge is recognized by most speaker inputs and therefore can be output to a speaker system.

DACs are also used for converting video signals. Historically, most video displays, such as TVs and computer monitors used analog inputs. Only in the last couple of years have digital displays with DVI and HDMI connections become commonplace. Therefore, in order for a computer to output to an analog display, the digital video signal must be converted to an analog signal. This is why all video cards with an analog output (such as a VGA connection) also include a DAC.

Any time a signal is converted from one format to another, there is a potential loss of quality. Therefore, it is important to have a high-quality DAC whether you are converting audio or video signals. The same holds true when performing the opposite conversion, which requires an analog-to-digital converter, or ADC.

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Daemon

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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Dashboard

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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Data

Computer data is information processed or stored by a computer. This information may be in the form of text documents, images, audio clips, software programs, or other types of data. Computer data may be processed by the computer's CPU and is stored in files and folders on the computer's hard disk.

At its most rudimentary level, computer data is a bunch of ones and zeros, known as binary data. Because all computer data is in binary format, it can be created, processed, saved, and stored digitally. This allows data to be transferred from one computer to another using a network connection or various media devices. It also does not deteriorate over time or lose quality after being used multiple times.

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Data Management

Example: "The systems administrator has been put in charge of the company's data management."

Data management refers to the way individuals, companies, and organizations manage computer data. It includes micro applications, such as data architecture and design, as well as macro applications, including data storage, access, and security. While computer data may be intangible, it can also be valuable. Therefore, it is important for all users to consider how they manage their data. This may involve taking steps such as backing up important files and encrypting personal information.

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Data Transfer Rate

The data transfer rate is commonly used to measure how fast data is transferred from one location to another. For example, a hard drive may have a maximum data transfer rate of 480 Mbps, while your ISP may offer an Internet connection with a maximum data transfer rate of only 1.5 Mbps.

Data transfer rates are typically measured in bits per second (bps) as opposed to bytes per second, which can be understandably confusing. Because there are eight bits in a byte, a sustained data transfer rate of 80 Mbps is only transferring 10MB per second. While this is confusing for consumers, Internet service providers must enjoy measuring data transfer rates in bps since it makes their Internet access speeds sound 8x faster than they really are.

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Data Type

A data type is a type of data. Of course, that is rather circular definition, and also not very helpful. Therefore, a better definition of a data type is a data storage format that can contain a specific type or range of values.

When computer programs store data in variables, each variable must be assigned a specific data type. Some common data types include integers, floating point numbers, characters, strings, and arrays. They may also be more specific types, such as dates, timestamps, boolean values, and varchar (variable character) formats.

Some programming languages require the programmer to define the data type of a variable before assigning it a value. Other languages can automatically assign a variable's data type when the initial data is entered into the variable. For example, if the variable "var1" is created with the value "1.25," the variable would be created as a floating point data type. If the variable is set to "Hello world!," the variable would be assigned a string data type. Most programming languages allow each variable to store a single data type. Therefore, if the variable's data type has already been set to an integer, assigning string data to the variable may cause the data to be converted to an integer format.

Data types are also used by database applications. The fields within a database often require a specific type of data to be input. For example, a company's record for an employee may use a string data type for the employee's first and last name. The employee's date of hire would be stored in a date format, while his or her salary may be stored as an integer. By keeping the data types uniform across multiple records, database applications can easily search, sort, and compare fields in different records.

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Database

Example: "Dynamic websites typically generate Web pages from data stored in a database."

A database contains data stored in a structured format. It includes one or more tables, which each contain multiple fields. Each field is assigned a specific data type, such as a string or integer. These fields include data for each record that is entered into the database. By storing data in organized records, the information in a database can be easily searched, sorted, and updated.

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DBMS

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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DDL

Example: "The DDL includes a "create" command that can be used to create a new database or table."

DDL is short for "Data Definition Language." It is used to define the structure of a database, including the tables, columns, and data types that it contains. The most common DDL is a subset of SQL, the Structured Query Language. However, DDLs can also be used to describe other types of data structures, including XML schemas and other data models.

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DDR

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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DDR2

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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Debug

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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Debugger

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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Default

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.