Null Definition When a variable has no value, it considered to be null. Having a null value is different than having a value of 0, since 0 is an actual value. However, when used in a boolean test, both null and zero result in a FALSE value. Programmers often use boolean tests to determine whether a variable has been given a value or not.

Dot Matrix Definition A dot matrix is a 2D matrix of dots that can represent images, symbols, or characters. They are used for electronic displays, such as computer monitors and LED screens, as well as printed output. In a dot matrix display, the images are estimated using a discrete set of dots instead of lines and shapes. Therefore, the more dots that are used, the more clear and accurate the image representation will be. For example, a 16x16 dot matrix can represent the letter "S" more accur...

DPI Definition Stands for "Dots Per Inch." DPI is used to measure the resolution of an image both on screen and in print. As the name suggests, the DPI measures how many dots fit into a linear inch. Therefore, the higher the DPI, the more detail can be shown in an image. It should be noted that DPI is not dots per square inch. Since a 600 dpi printer can print 600 dots both horizontally and vertically per inch, it actually prints 360,000 (600 x 600) dots per square inch. Also, since most monit...

Resolution Definition Resolution measures the number of pixels in a digital image or display. It is defined as width by height, or W x H, where W is the number of horizontal pixels and H is the number of vertical pixels. For example, the resolution of an HDTV is 1920 x 1080. Image Resolution A digital photo that is 3,088 pixels wide by 2,320 pixels tall has a resolution of 3088 × 2320. Multiplying these numbers together produces 7,164,160 total pixels. Since the photo contains just over seven mi...

Macintosh Definition Macintosh is a line of desktop and laptop computers developed by Apple. Each Macintosh computer, or Mac, runs a version of the Mac OS, Apple's desktop operating system. Since 2001, all Macs have run Mac OS X, a redesigned version of the original Mac OS that was built from the NeXTSTEP operating system. The original Macintosh, released in 1984, was the first personal computer to have a graphical user interface, or GUI. It was in all-in-one machine with a color display and in...

Logic Gate Definition Logic gates perform basic logical functions and are the fundamental building blocks of digital integrated circuits. Most logic gates take an input of two binary values, and output a single value of a 1 or 0. Some circuits may have only a few logic gates, while others, such as microprocessors, may have millions of them. There are seven different types of logic gates, which are outlined below. In the following examples, each logic gate except the NOT gate has two inputs, A a...

LTE Definition Stands for "Long Term Evolution." LTE is a 4G telecommunications standard used for transferring data over cellular networks. It supports data transfer rates of up to 100 Mbps downstream and 50 Mbps upstream. While the terms "4G" and "LTE" are often used synonymously, LTE is actually a subset of 4G technologies. Other 4G standards include Mobile WiMAX (IEEE 802.16e) and WirelessMAN-Advanced (IEEE 802.16m). However, since LTE was designed to be an international telelcommunications ...

Input Definition Whenever you enter data into your computer, it is referred to as input. This can be text typed in a word processing document, keywords entered in a search engine's search box, or data entered into a spreadsheet. Input can be something as simple as moving the mouse or clicking the mouse button or it can be as complex as scanning a document or downloading photos from a digital camera. Devices such as the keyboard, mouse, scanner, and even a digital camera are considered input dev...

IT Definition Stands for "Information Technology," and is pronounced "I.T." It refers to anything related to computing technology, such as networking, hardware, software, the Internet, or the people that work with these technologies. Many companies now have IT departments for managing the computers, networks, and other technical areas of their businesses. IT jobs include computer programming, network administration, computer engineering, Web development, technical support, and many other related...

Password Definition A password is a string of characters used for authenticating a user on a computer system. For example, you may have an account on your computer that requires you to log in. In order to successfully access your account, you must provide a valid username and password. This combination is often referred to as a login. While usernames are generally public information, passwords are private to each user. Most passwords are comprised of several characters, which can typically incl...