Dictionary of Technology Terms


The entries in this dictionary are not typical definitions. By a typical definition, I mean a definition that tells you just what a term means and no more. Because the purpose of this dictionary is to help the students and staff of the Smyth County School System master technology, I have made the definitions mini-essays on technology, with lots of examples on how we use that technology in our school system. I started this dictionary in the pre-Wikipedia days, when it was much harder to find accurate information on technology terms. Today, I strongly recommend that you consult Wikipedia to learn more about technology terms.

To use the dictionary, click one of the letters below to immediately jump to words beginning with that letter, or choose Find from the Edit Menu and type the word you are looking for.

This dictionary is always growing. If you encounter a term you are unfamiliar with, send it to me and I will research and post the definition. If you would like to contribute an essay, please let me know. Contributors to the dictionary are credited with a byline. If there is no byline, I am responsible for the essay and any errors it may contain.

--Terry Hawthorne



This word is used in the telecommunications and distance learning fields. It has a similar meaning in both fields. In telecommunications, it refers to an exchange of data at intermittent, or non-synchronized intervals between two devices. In the distance learning field, it refers to learning systems in which the instructor and students do not have to synchronize their presence. The use of Web-based discussion boards is an asynchronous distance learning activity, because the students and instructor can post their thoughts to the board at any time. The SVETN electronic classrooms and the Holton Governor's School LearnLinc system are synchronous distance leaning activities, because they require the facilitator and students to synchronize their presence.
Asynchronous Transfer Mode. This is a networking technology used to transfer computer data, voice, and video across local area networks and wide area networks. ATM can be used be used to create a single, unified network that can carry computer data, voice, and video from your desktop computer to anywhere in the world. However, it is more expensive than traditional local area network technologies such as Ethernet, so today it is mainly used for connecting computers across great distances.


Bits per second. This measures how much data can be transferred across a network connection. A bit is the smallest unit of information that computers deal with. Today we usually measure bps in kilobits per second or megabits per second. A kilobit is 1,000 bits, and a megabit is 1,000,000 bits. If you are reading this page from a computer located in one of Smyth County's elementary or middle schools, your connection speed is between 3 and 5 megabits per second. If you are reading it from a computer located in one of our three high schools, your connection speed is 100 megabits per second. The connection speed is called bandwidth. We have more bandwidth in our high schools because we have high school students taking distance learning classes over our internal network and the Internet, and they need the additional bandwidth for those classes.
The software that you are using to view this page. A browser is also called a Web browser, because it is used to browse the content of the World Wide Web. The most popular browsers are Microsoft's Internet Explorer, Mozilla Firefox, Google Chrome, and Apple Safari. Today's Graphical User Interface (GUI) browsers trace their ancestry back to Mosaic, the original graphical browser developed at the National Center for Supercomputing Applications at the University of Illinois. GUI browsers can display text, images, digital movies, sound, and other multimedia content. The original Web browsers could only display text.


Abbreviation for computer-assisted design, or computer-assisted drafting. Architects, designers, draftsmen, and engineers use CAD software to create drawings for buildings, products, and other designs. Some CAD software has three-dimensional capabilities that enable users to create realistic computer-generated versions of their designs for virtual walkthroughs. CAD is among the career and technical courses offered in Smyth County schools.
Upper-case letters. When you press the Caps Lock key on your keyboard, it makes everything you type upper-case. In the early days of computing, many computers had no way of representing lower-case and upper-case letters, but all computers today have that capability. You should avoid typing a message in all caps, because it makes the text harder to read.
cellImage of spreadsheet depicting cell.
The box in a spreadsheet that occurs at each intersection of a row and column. You can use a cell to store text, number, formulas, or dates. See the picture at the right.
A area of computer memory set aside for storing temporary copies of text, images, or other information, so that information can be copied from one document to another.
cloud computing
Computing that relies on networked storage or web applications is referred to as cloud computing. The name comes from the cloud shape traditionally used in network diagrams to refer to the Internet or another large network. Gmail and other Google Apps are an example of cloud computing.
A person who tries to break into other people's computers, usually across the Internet. There are federal and state laws against cracking. Kevin Mitnick, probably the most famous computer cracker in history, was held in federal custody without bail for several years, while awaiting trial for his cracking exploits.
The blinking line that marks your place in a document. When you begin typing, text will appear at the cursor's location. Database professionals use the term cursor to refer to a set of records that is retrieved from a database through an embedded SQL statement. If you have used Virginia's Educational Information Management System (EIMS) or PEM Solutions to retrieve test records, you have worked with a database cursor.
To copy text, images, or other information from a document into the computer's clipboard memory, while deleting the original information. Compare this to copy, in which the information is copied to the computer's clipboard memory, without deleting the original information.


data warehouse
A data warehouse is a database that is structured for reporting and querying. Most data warehouses are built on the principles developed by Ralph Kimball. Data warehouses extract information from a variety of sources, including transactional database systems; e.g. student information systems, clean and transform that data, then load it into a series of fact tables and dimension tables. The front end of the data warehouse provides end users with access to the data through pre-defined reports or tools that enable advanced users to slice and dice the data in many ways.
An HTML tag that is not supported in the latest specficiation of the HTML language. For example, tags that refer to appearance, such as bgcolor and font, are deprecated in the latest HTML specification.
Domain Name System, a distributed database that maps computer hostnames such as www.scsb.org to IP addresses. Computers that access the Internet need to be configured with the addresses of one or more DNS servers. Most computers receive their DNS server addresses through DHCP (Dynamic Host Configuration Protocol), the protocol used to automatically assign computers an IP address, subnet mask, and default gateway.


Encryption is the process of encoding information to prevent it from being read by unauthorized individuals. Human beings have been encypting documents for centuries. In the 20th Century, nations and organizations began to use mechanical methods to improve their encryption methods; e.g., the German Enigma machine. In response, cryptanalysts (people who study and break encyption schemes) developed early computers to help them break the codes. Since that time, computer scientists and mathematicians have developed encryption methods based on a public/private key algorithm. These methods enable secure online communications for a variety of applications, such as electronic commerce, remote computer access, and email.
Ethernet is a telecommunications protocol. We use it to connect computers to the local area network in our schools.


In a building, a firewall is a wall that is used to contain the damage caused by a fire. In computing, a firewall is software or hardware that is used to contain the potential damage that can result from connecting your computer network to a public network, such as the Internet. Hackers and crackers use the Internet to attempt to break into private computer networks that are connected to the Internet. In Smyth County, we use a firewall to keep the hackers and crackers out of our network.
To change the size, font, color, or other characteristics of information stored in a computer. Format can also mean the way that computer programs organize and store information. For example, the file that you are reading right now is in Hypertext Markup Language (HTML) format. Format can also mean to prepare a disk or USB drive to accept information.
frame relay
Frame relay is a method of connecting computers across a great distance. Frame relay service is usually provided by the local telephone company. It is less expensive and usually provides faster transfers than a leased telephone line. Leased telephone lines used to be the most popular way of connecting computers at different sites.
File Transfer Protocol. This technology is used to transfer files between computers that are running the TCP/IP protocol suite. When you download a file from the Internet, you may use ftp. The most common type of ftp service is called anonymous ftp. This enables anyone to download files from an ftp server. In Smyth County, school Web site authors use ftp to transfer their Web pages to the school board's Web server. Please note that, although ftp is an abbreviation, it is commonly spelled with lowercase letters. This can be traced back to its roots in the Unix world, where filenames are case-sensitive (to a Unix computer, FTP is not the same thing as ftp), and ftp was always lowercase.


GIF is one of the three most common graphics files formats used on the Internet. (JPEG and PNG are the others.) Internet browsers can display GIF files without any plug-ins or helper applications. The maximum number of colors that can be used in a GIF file is 256. This makes them best suited for drawings, charts, and other images which have large areas of flat color and distinct boundaries between colors. The JPEG format is better suited for full-color photographs. GIF and JPEG both use compression techniques to reduce the file size of the graphics they store. GIF uses lossless compression. GIF stands for Graphics Interchange Format.
A billion bits. New computers have network interface cards capable of transmitting and receiving data at one gigabit per second.
A digital picture, chart, or other image.


A standards-based technology for delivery real-time audio and video over packet-based networks, such as the Internet. The Smyth County School and the Smyth-Bland Regional Library have H.323-based video conferencing rooms, and the Southwest Virginia Education & Training Network (SVETN) uses H.323 to connect its classrooms.
In the early days of computing, calling someone a hacker was a compliment. A hacker was someone who thoroughly understood how computers worked and was able to make them do all sorts of things that they may not have been designed to do. An elegant piece of programming was called a hack. Today, hackers are thought of as outlaws: computer users who try to break into other people's computers. See cracker.
The default Web page that a browser displays when you start it. Modern browsers have the ability to display multiple home pages through a tabbed interface.
HyperText Markup Language. HTML consists of a set of tags for formatting World Wide Web pages. The tags control how your browser displays the page. For example, the text you are reading now is a definition. It is enclosed by <dd> and </dd> tags. A browser usually displays definition text by indenting it slightly from the left margin. Other tags are more complex. For example, the tag to display a picture might be: <img src="filename.jpg" height="100" width="200" alt="This text appears if the browser does not display pictures, or before the picture is loaded." />
HyperText Transfer Protocol. HTTP is the protocol upon which the World Wide Web is built. Tim Berners-Lee developed HTTP in the late 1980s to enable scientists to publish and share hypertext documents.


ICQ was the first popular instant messaging software. Instant messaging software enables users to communicate by sending typed messages back and forth. It differs from e-mail in that instant messaging software can tell you when your friends are on-line, so you can send them messages and receive responses right away. ICQ still exists and has adapted to the mobile world by developing ICQ apps for both the iPhone and Android operating systems.
immersive photography
Image you could take a photograph that includes a complete 360 field of view. This is the field of view that teachers who have eyes in the back of their heads see;) Wrap that photograph around a transparent cylinder. Now imagine that you could shrink yourself and stand inside that cylinder. As you turn around, you would see the 360 scene from the same position as the photographer who made the picture. That is immersive photography. Apple Computer was the first company to demonstrate this, using QuickTimeVR technology.
The largest computer network in the world. You are using the Internet to read this document. If you are connecting to this page from a computer located in a Smyth County school, you are not actually on the Internet. Only a small number of computers in the Smyth County school system are actually on the Internet; all of the rest access the Internet through a proxy server located on the school system's intranet.
An intranet is a private computer network that uses the same technology as the Internet. For example, Smyth County schools are connected to the Central Office by an intranet. The advantage of an intranet is that we offer Internet access to all of our schools without exposing their computers or network to the Internet itself. We accomplish this through a proxy server. An intranet also lets us use Web browsers to share information that we don't want to post on the Internet.


A object-oriented computer programming language developed by Sun Microsystems. People are excited about Java because it represents a platform-independent language. In theory, you can write a program in Java and run it on a Linux, Macintosh, Unix, or Windows computer. The key to this platform independence is that Java programs run in what Sun calls a Java Virtual Machine, or JVM. Once a computer manufacturer writes a JVM for its computers, in theory any Java program could run on that JVM. In practice that is not always the case. TestNav, the secure browser used by the Virginia Department of Education for online Standards of Learning assessments, is written in Java. Java is also very popular in university computer science departments.
A computer scripting language that is most frequently used for adding interactivity to Web pages and validating data entry on web forms prior to their submission.
JPEG is one of the three most common graphics files formats used on the Internet. (GIF and PNG are the others.) Internet browsers can display JPEG files without any plug-ins or helper applications. JPEG files are best suited for full-color images. JPEG uses a lossy compression method to reduce the size of the images it stores. (Lossy means that the the compression technique works by discarding some of the information in the picture. JPEG technology allows for variable compressions schemes; that is, you can achieve smaller file sizes by using more compression, at the expense of picture quality.
A library of Javascript functions. The JQuery library simplifies web application development by making available a large number of commonly used functions for purposes such as animation and event handling in a single, compact Javascript file.


A kilobit is 1,000 bits.
A kilobyte is 1,024 bytes. Why is a kilobit 1,000 bits and a kilobyte 1,024 bytes? The prefix kilo means 1,000, so a kilogram is 1,000 grams, and a kilometer is 1,000 meters, and a kilobit is 1,000 bits. In computer science, the term kilobit is used as a measure of network bandwidth. The term kilobyte is used as a measure of storage. For example, a file may take up 100 kilobytes of disk space. Since a kilobyte is 1,024 bytes, that file takes up 102,400 bytes. The reason computer scientists use 1,024 rather than 1,000 comes from the fact that storage locations in a computer have binary addresses; that is, they can be expressed as powers of two. For example, 210 = 1,024, or approximately 1,000. Please note that this distinction is not practiced uniformly, especially by the manufacturers of disk drives and USB drives. When they refer to kilobytes, megabytes, and gigabytes, they intend for those prefixes to mean one-thousand, one-million, and one-billion. This means they can advertise their devices as having more storage capacity than they would if they used the kilo, mega, and giga prefixes with their binary meanings.


Acronym for Linux-Apache-MySQL-PHP. A LAMP system is a computer running the Linux operating system, the Apache web server, the MySQL relational database management system, and the PHP (or Python or Perl) programming language interpreter. These four open-source applications provide an inexpensive, robust, and high-performance platform for developing web applications. Variations include WAMP, which substitutes the Windows operating system for Linux; MAMP, which substitutes Mac OSX for Linux;and XAMPP, an Apache Friends project that bundles all of this software into an easily installed distribution.
Local Area Network. Each school in Smyth County has one or more LANs. Computers in classrooms, libraries, offices, and labs are connected to the LAN by a network interface card (NIC) and Category 5 cabling. Here are some common and potential uses for our LANs.
Library Catalog Browsing All of the libraries in Smyth County schools use the Alexandria Library Automation System. One of Alexandria's features is an on-line catalog. By placing the client software for this on computers throughout a school, students and staff can search the library's holdings.
Assessments Each year we deliver approximately 11,500 online SOL tests to students. We also use our networks to deliver Interactive Achievement tests, Criterion writing tests, Accelerated Reader quizzes, and other types of assessments.
Internet Access Internet access through the LAN is much faster than the dial-up access we used to use. There is no waiting to establish a dial-up connection, and there are no dropped connections with a LAN connection. The cost is also lower on a per-computer basis. We are also able to filter all Internet connections at a single point, rather than having to install filtering software on every computer.
Distance Learning We have distance learning programs in place with the A. Linwood Holton Governor's School, SVETN's Elite Learning Program, and the Virginia Virtual AP School. All of these programs use networks to connect teachers and students.
E-Mail Every administrator and teacher has an email account, as well as students who need email for their distance learning courses.


A megabit is one million bits.
A megabyte is 1,048,576 bytes (1,024 x 1,024). Please refer to the discussioin of kilobits and kilobytes for clarification.
The abbreviation for MPEG-1 or MPEG-2 Audio Layer III, which is a patented format used to encode compressed digital audio. The term is commonly used to refer to songs that have been encoded in this format. The MP3 format enables a uncompressed digital audio file to be significant reduced in size, at the loss of some audio quality. The MP3 format is the de facto format for portable digital audio players, although most players sold today support other audio formats as well, such as Windows Media, AAC (the default format for iPods), or the open-source Ogg Vorbis format.


An abbreviation for network.
A group of computers, printers, and other devices that are connected together to exchange information. When used as a verb, network means the act of joining computers, printers, and other devices together; or the act of joining a computer to an existing network. We use our school network to record attendance and grades, check library books in and out, do research, share printers, and exchange e-mail.


Optical Character Recognition. OCR software is capable of converting a digital image of a page of scanned text into editable text. The degree of accuracy varies with the quality of the original text. OCR works well with clean copy produced by a typewriter or a printer; it works very poorly with handwritten text.
Open Database Connectivity, a standard software interface for accessing database management systems, such as Oracle, SQL Server, or MySQL. In Smyth County Schools, we use ODBC to connect directly to our student information system's underlying Oracle database from a Microsoft Access front end. This enables us to use Access's graphical query designer and report writer to access data stored in the Oracle data tables.
open source
Software of which the source code is free available to the general public. Open source software is also available to freely download and use. Examples of open source software include:
  • The Linux operating system
  • The OpenOffice and LibreOffice office productivity suites
  • The Apache web server
  • The MySQL relational database management system
  • The GIMP image editing program
  • The PHP, Python, and Perl programming languages
optical drive
A CD-ROM drive, DVD drive, or other device that uses a laser to record and/or write data onto an optical disk. Read-only and ready-write optical drives have been the workhorses of removeable data storage for a number of years, but are gradually being supplanted by USB drives and cloud-based storage.


Peer-to-Peer Network

A peer-to-peer network, usually abbreviated p2p, is a group of network nodes or devices that can share content with one another. Many file-sharing sites are implemented as p2p networks. The Recording Industry Association of America (RIAA) has filed lawsuits against some of these sites whose primary purpose is to enable members to share copyrighted multimedia files, such as songs and movies.
1,000,000 gigabytes. In the International System of Units (SI), peta means 1015, so 1 petabyte = 1,000,000,000,000,000 bytes. Some very large databases occupy multiple petabytes of disk space.


Quality of Service, a technology used to provide guaranteed bandwidth and priority for time-sensitive network applications, such as video conferencing.


Relational Database Management System. An RDBMS is software that manages relational databases; that is, databases that consist of a number of related tables that model some real-world system. RDBMS software enables users to create tables that can store millions of rows of information, enforce referential integrity rules on the information stored in those tables, and query the data stored in those tables. Common RDBMSs include Microsoft Access and SQL Server, Oracle, IBM's DB2, and the open-source MySQL and PostgresSQL systems.
referential integrity
A database concept that ensures that relationships between tables in an RDBMS remain consistent. An example will make this concept clearer. Suppose you have a database to track student attendance. In that database there is a students table, in which each row represents an individual student. The primary key for that table would be the student ID number. (A primary key is a field in a table that uniquely identifes each row in the table. In the case of the students table, this means that each student has a unique ID number, and the database will not permit a duplicate number to be entered.) In the attendance table, we would have columns to store the student ID, the date, and an attendance code; e.g., P=Present, A=Absent, etc. Referential integrity means that there cannot be any row in the attendance table containing a student ID that is not already present in the students table. Referential integrity gives the database designer a way to enforce a real-world constraint. In this case, the constraint is that you cannot create an attendance record for a student who does not exist.
A router is a specialized computer that connects local area networks to wide area networks. Each school in Smyth County uses a router, or routing software running on a high-speed network switch, to connect to other schools and the Central Office.


A device that converts a picture, printed text, a barcode, or some other physical form of information into a digital form that a computer can read. Scanners are commonly used to convert photographs into digital images. Libraries use scanners to read the barcodes on books when they are checked out and in, and supermarkets use scanners to read the barcodes on shoppers' purchases.
search engine
A Web site that enables users to search for Web pages by entering keywords. Yahoo was the first successful search engine. When you create a Web site, it does not automatically appear in a search engine's index. Most search engines enable you to add your site to their index, with your choice of keywords. Search engines also use software that roams the World Wide Web, automatically indexing new sites. For example, this Web site shows upon the Google search engine, even though I have not registered it with Google.
streaming audio
Streaming audio solves a problem that used to discourage the use of sound on the Internet. Before streaming audio, Web users had to download an entire sound file before they could hear it. Because sound files tend to be fairly large, users had to wait a long time before they could hear the file. Web browsers can begin playing streaming audio files a few seconds after the download begins. In other words, you hear the file as it streams into your computer, rather than after it arrives. Streaming video does the same thing for digital movies, which are even bigger than digital sound files.


Transmission Control Protocol/Internet Protocol, the world's most popular computer networking protocol. TCP/IP is actually a suite of several different protocols: TCP, IP, FTP, HTTP, etc.
1,000 gigabytes. In the International System of Units (SI), tera means 1012, so 1 terabyte = 1,000,000,000,000 bytes. Disk drives of 1 terabyte or larger have now become commonplace.


Uniform Resource Locator. This is the basic addressing scheme used by the World Wide Web. For example, the URL of this page is http://www.scsb.org/glossary.html. This address consists of several parts:
Protocol http:// The protocol is the method that will be used to retrieve the page. http means HyperText Transfer Protocol, which is the standard protocol for Web pages. URLs also support older protocols, such as ftp, and newer protocols such as https (secure http). Timesaving Tip: When you enter a URL into your browser's address window, you don't have to type http://. This is the default protocol, and your browser will insert it automatically.
Hostname www Computers that serve Web pages and other Internet content usually have a host name, which is easier for humans to remember than the computer's numeric address. For example, the file you are currently reading is stored on a computer named www. A common misunderstanding among some Internet users is that all web pages and applications have to be stored on computers named www. Not so; for example, our student information system is a web application, and it is housed on a computer named sis01.
Domain name scsb The domain name is the name officially registered to a company or organization by the InterNIC, the organization in charge of assigning Internet names. Our domain name means Smyth County School Board.
Top-level domain org The top-level domain indicates the type of organization that owns the domain name. The org domain is for non-profit organizations. The com domain is for profit-making businesses. Other top-level domains are edu for universities, mil for military, gov for government, and net for Internet-related organizations. Note that these top-level domains apply to organizations within the United States. In other countries, the top-level domain represents the country.
Filename glossary.html This is the filename of the actual page returned by your browser. It is a plain text file residing on our Web server. If you don't include a filename, the Web server will return the default page, which is probably named default.html or index.html.


The process of creating virtual machines, or guest computers that run entirely within virtualization software. Server virtualization is a popular technology for reducing hardware and operating costs while increasing reliability and uptime. A common server virtualization configuration employs multiple servers running software called a hypervisor that enables the servers to host a number of virtual operating systems. The virtual systems, called guests, could be Windows, Linux, or some other type of operating system, depending on the hypervisor software's capabilities. The multiple hardware servers provide failsafe redundancy for their guests. If one of the physical servers fails, the guests it was hosting can simply be restarted on another of the physical servers, while the failed server is being replaced.
A malicious computer program that secretly installs itself on a computer or attachs itself to one or more files running on a host computer. Strictly speaking, a computer virus has the ability to copy itself and infect other computers across a network or through shared media, such as USB drives. More commonly, virus is used as a catch-all phrase for any type of undesirable program, such as adware, malware, or fake anti-virus software. You can avoid most viruses and other malware by installing a reputable anti-virus program and keeping its virus definitions updated, and by following other safe computing practices


The World Wide Web is the most popular Internet information service. It is so popular that many Internet newcomers think that it is the Internet. It is, however, another Internet service like electronic mail and ftp. Ease of use made the World Wide Web popular, and the staggering amount of information available on it will ensure that its popularity increases.
Any technology that uses radio or light waves to transmit and receive information. We use the IEEE's 802.11 wireless networking protocols to connect laptop labs to our local area networks. During the first years of the 21st century, we also used wireless technology to connect Marion Intermediate, Marion Middle, Marion Primary, and Marion Senior High schools to our wide area network; however, as more homeowners and businesses installed wireless networking gear we began to experience increased interference on those networks, which prompted us to switch to more robust fiber connections. In general, the use of wireless networking technology, especially in the unlicensed frequencies used by consumers and most organizations, is a matter of convenience and a way to extend computer networks to locations where wired connections are impractical. That convenience must be weighed against the greatly reduced bandwidth provided by wireless networks compared to wired networks.


x y z coordinates
A method of identifying points in a three-dimensional Cartesian coordinate system. Any point in a system like this can be identified by its x coordinate (its horizontal distance from the 0,0,0 origin), its y coordinate (vertical distance), and z coordinate, which represents depth. Three-dimensioinal Cartesian coordinate systems are used in 3D modeling programs, such as Blender.