SCIENCE DIRECT

INTELLIGENT TERMINAL: A terminal (monitor and keyboard) that contains processing power. Intelligent terminals include memory and a processor to perform special display operations. In contrast, a dumb terminal has no processing capabilities; it must rely entirely on the central computer. A smart terminal has some processing capabilities, but not as much as an intelligent terminal. INTERLACING: A display technique that enables a monitor to provide more resolution inexpensively. With interlacing monitors, the electron guns draw only half the horizontal lines with each pass (for example, all odd lines on one pass and all even lines on the next pass). Because an interlacing monitor refreshes only half the lines at one time, it can display twice as many lines per refresh cycle, giving it greater resolution. Another way of looking at it is that interlacing provides the same resolution as noninterlacing, but less expensively. A shortcoming of interlacing is that the reaction time is slower, so programs that depend on quick refresh rates (animation and video, for example), may experience flickering or streaking. Given two monitors that offer the same resolution, the noninterlacing one will generally be better. Preparing a graphic image so that alternating rows are displayed in separate passes. Interlaced images give a nice effect because the entire image is displayed quickly and then details are filled in gradually. They are especially prevalent on the World Wide Web because of the slow transmission speed. Web pages with interlaced GIFs appear in a browser more quickly than pages with normal GIF images. The interlaced GIFs look blurry at first, but then become sharp as the rows are filled in. LCD: Abbreviation of liquid crystal display, a type of display used in digital watches and many portable computers. LCD displays utilize two sheets of polarizing material with a liquid crystal solution between them. An electric current passed through the liquid causes the crystals to align so that light cannot pass through them. Each crystal, therefore, is like a shutter, either allowing light to pass through or blocking the light. Monochrome LCD images usually appear as blue or dark gray images on top of a grayish-white background. Color LCD displays use two basic techniques for producing color: Passive matrix is the less expensive of the two technologies. The other technology, called thin film transistor (TFT) or active-matrix, produces color images that are as sharp as traditional CRT displays, but the technology is expensive. Recent passive-matrix displays using new CSTN and DSTN technologies produce sharp colors rivaling active-matrix displays. Most LCD screens used in notebook computers are backlit to make them easier to read in bright environments. MASK PITCH: In color monitors, the distance between phosphors of the same color. The mask pitch is generally about 30 millimeters (mm). The tighter the mask pitch, the sharper the image. MCGA: Abbreviation of multicolor/graphics array (or memory controller gate array), the graphics system built into some older PCs. It provides graphics capabilities equal to or greater than MDA and CGA, but it is not as powerful as EGA or VGA. Like VGA, MCGA uses analog signals. MDA: Abbreviation of monochrome display adapter, an old monochrome video standard for PCs. MDA supports high-resolution monochrome text but does not support graphics or colors. The resolution for text is 720 by 350 pixels. MONOCHROME: One color. Monitors, for example, can be monochrome, grayscale or color. Monochrome monitors actually use two colors, one for the display image (the foreground) and one for the background. Graphic images can also be monochrome, grayscale, or color. MULTIFREQUENCY MONITOR: A type of video monitor capable of accepting signals at more than one frequency range. This enables the monitor to support several different video standards. Typically, multifrequency monitors for PCs support MDA, Hercules, CGA, VGA, and sometimes SVGA. Multifrequency monitors differ somewhat from multiscanning monitors. Multiscanning monitors can support video signals at any frequency level within its range, whereas multifrequency monitors support only a select number of frequency levels. However, because almost all video signals conform to one of a handful of video standards, the greater potential of multiscanning monitors is generally not utilized. MULTISCANNING MONITOR: A type of monitor that automatically adjusts to the signal frequency of the video display board to which it is connected. Consequently, multiscanning monitors can display images based on almost any graphics display system, including MDA, Hercules, EGA, VGA, and SVGA. In contrast, fixed-frequency monitors respond to only one, or a few, frequencies, so they can connect to a limited number of video display boards. However, fixed-frequency monitors are less expensive than multiscanning monitors and sometimes produce sharper images. Multiscanning monitors are also called multisync, multifrequency, and variable-frequency monitors. Increasingly, however, the term multifrequency monitor is reserved for monitors that support a fixed number of video frequencies. In contrast, multiscanning monitors scan the incoming signals and set themselves to whatever frequency range they are receiving. In practice, there is little difference between the two types of monitors because most video signals conform to one of a handful of video standards. NON-INTERLACED: Refers to monitors and video standards that do not use interlacing techniques to improve resolution. Although interlacing increases resolution, it also increases screen flicker and reduces reaction time. PAPER-WHITE DISPLAY: A high-quality monochrome monitor that displays characters in black against a white background. Such monitors are popular for desktop publishing because they most closely mimic real paper with black type. Some manufacturers make a distinction between normal white-background monitors and paper-white monitors, where the background is slightly tinted to look more like bonded paper. PASSIVE-MATRIX DISPLAY: A common type of flat-panel display consisting of a grid of horizontal and vertical wires. At the intersection of each grid is an LCD element which constitutes a single pixel, either letting light through or blocking it. A higher quality and more expensive type of display, called an active-matrix display, uses a transistor to control each pixel. In the mid-90s, it appeared that passive-matrix displays would eventually become extinct due to the higher quality of active-matrix displays. However, the high cost of producing active-matrix displays, and new technologies such as DSTN and CSTN that improve passive-matrix displays, have cause passive-matrix displays to make a surprising comeback. PIXEL: Short for Picture Element, a pixel is a single point in a graphic image. Graphics monitors display pictures by dividing the display screen into thousands (or millions) of pixels, arranged in rows and columns. The pixels are so close together that they appear connected. The number of bits used to represent each pixel determines how many colors or shades of gray can be displayed. For example, an 8-bit color monitor uses 8 bits for each pixel, making it possible to display 2 to the 8th power (256) different colors or shades of gray. On color monitors, each pixel is actually composed of three dots -- a red, a blue, and a green one. Ideally, the three dots should all converge at the same point, but all monitors have some convergence error that can make color pixels appear fuzzy. The quality of a display monitor largely depends on its resolution, how many pixels it can display, and how many bits are used to represent each pixel. VGA monitors display 640 by 480, or about 300,000 pixels. In contrast, SVGA monitors display 1,024 by 768, or nearly 800,000 pixels. True Color monitors use 24 bits per pixel, allowing them to display more than 16 million different colors. PLASMA DISPLAY: A type of flat-panel display that works by sandwiching an ionized gas between two wired panels. In one panel the wires are placed in vertical rows, and in the other they are placed in horizontal rows. Together, the two panels form a grid. An individual point (pixel) can then be charged by passing a current through the appropriate x-coordinate and y-coordinate wires. When the gas is charged, it glows a bright orange. RESOLUTION: Refers to the sharpness and clarity of an image. The term is most often used to describe monitors, printers, and bit-mapped graphic images. In the case of dot-matrix and laser printers, the resolution indicates the number of dots per inch. For example, a 300-dpi (dots per inch) printer is one that is capable of printing 300 distinct dots in a line 1 inch long. This means it can print 90,000 dots per square inch. For graphics monitors, the resolution signifies the number of dots (pixels) on the entire screen. For example, a 640-by-480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. For example, a 15-inch VGA monitor (640x480) displays about 50 dots per inch. Printers, monitors, scanners, and other I/O devices are often classified as high resolution, medium resolution, or low resolution. The actual resolution ranges for each of these grades is constantly shifting as the technology improves REVERSE VIDEO: A display method that causes a portion of the display to appear like a negative of the regular display. If the display screen normally displays light images against a dark background, putting it in reverse video mode will cause it to display dark images against a light background. Many programs use reverse video to highlight items, such as selected text or menu options. Also, some systems allow you to change the mode for all displays, so you can choose the display that is most comfortable for you. Some people prefer dark images on a light background, while others prefer light images on a dark background. RGB MONITOR: Short for red, green, blue monitor, a monitor that requires separate signals for each of the three colors. This differs from color televisions, for example, which use composite video signals, in which all the colors are mixed together. All color computer monitors are RGB monitors. An RGB monitor consists of a vacuum tube with three electron guns -- one each for red, green, and blue -- at one end and the screen at the other end. The three electron guns fire electrons at the screen, which contains a phosphorous coating. When the phosphors are excited by the electron beams, they glow. Depending on which beam excites them, they glow either red, green, or blue. Ideally, the three beams should converge for each point on the screen so that each pixel is a combination of the three colors. SCREEN FLICKER: The phenomenon whereby a display screen appears to flicker. Screen flicker results from a variety of factors, the most important of which is the monitor's refresh rate, the speed with which the screen is redrawn. If the refresh rate is too slow, the screen will appear to glimmer. Another factor that affects screen flicker is the persistence of the screen phosphors. Low-persistence phosphors fade more quickly than high-persistence monitors, making screen flicker more likely. Screen flicker can also be affected by lighting. Finally, screen flicker is a subjective perception that affects people differently. Some people perceive screen flicker where others do not. SCREEN SAVER: A small program that takes over the display screen if there are no keystrokes or mouse movements for a specified duration. Screen savers were originally developed to prevent ghosting, the permanent etching of a pattern on a display screen. For older monochrome monitors, ghosting often occurred if the same pattern was displayed on a display screen for a long period of time. Screen savers would prevent this by either blanking out the screen entirely or by displaying a constantly moving image. Modern display screens do not suffer so much from this problem. Today, therefore, screen savers are mostly an adornment, a way to liven up the computer. Many screen savers provide another benefit, hiding a user’s work from would-be snoopers. These screen savers fill the display with an image or animation until the user enters a password. SCROLL: To view consecutive lines of data on the display screen. The term scroll means that once the screen is full, each new line appears at the edge of the screen and all other lines move over one position. For example, when you scroll down, each new line appears at the bottom of the screen and all the other lines move up one row, so that the top line disappears. The term vertical scrolling refers to the ability to scroll up or down. Horizontal scrolling means that the image moves sideways. In theory, the display should move smoothly, as if it were a piece of paper being moved up, down, or sideways. In practice, however, scrolling is not always so smooth.The scrolling method of viewing documents does not recognize page boundaries. One advantage to scrolling, therefore, is that you can look at the end of one page and the beginning of the next page at the same time. Another method of viewing data is called paging, whereby an entire page is displayed at once. Each subsequent page replaces the previous page on the screen. SMART TERMINAL: A terminal that has some processing capabilities, but not as many as an intelligent terminal. Smart terminals have built-in logic for performing simple display operations, such as blinking and boldface. In contrast, a dumb terminal has no processing capabilities at all. SUPERTWIST: A technique for improving LCD display screens by twisting light rays. In addition to normal supertwist displays, there also exist double supertwist and triple supertwist displays. In general, the more twists, the higher the contrast.Supertwist displays are also known as supertwist nematic (STN) displays. SVGA: Short for Super VGA, a set of graphics standards designed to offer greater resolution than VGA. There are several varieties of SVGA, each providing a different resolution: · 800 by 600 pixels · 1024 by 768 pixels · 1280 by 1024 pixels · 1600 by 1200 pixels All SVGA standards support a palette of 16 million colors, but the number of colors that can be displayed simultaneously is limited by the amount of video memory installed in a system. One SVGA system might display only 16 simultaneous colors while another displays the entire palette of 16 million colors. The SVGA standards are developed by a consortium of monitor and graphics manufacturers called VESA. TERMINAL: A device that enables you to communicate with a computer. Generally, a terminal is a combination of keyboard and display screen. Terminals are sometimes divided into three classes based on how much processing power they contain: intelligent terminal: A stand-alone device that contains main memory and a CPU.smart terminal: Contains some processing power, but not as much as an intelligent terminal.dumb terminal: Has no processing capabilities. It relies entirely on the computer's processor. In networking, a terminal is a personal computer or workstation connected to a mainframe. The personal computer usually runs terminal emulation software that makes the mainframe think it is like any other mainframe terminal. TIGA: A high-resolution graphics specification designed by Texas Instruments. Unlike other graphics standards, TIGA does not specify a particular resolution or number of colors. Instead, it defines an interface between software and graphics processors. Programs written for TIGA, therefore, should be able to run on future systems that conform to the TIGA standard, regardless of resolution and color specifics. Currently, the only graphics standard that conforms to TIGA is TI 34010, which defines a resolution of 1,024 by 768, with 256 simultaneous colors. Two competing standards with the same resolution are 8514/A from IBM and SVGA from VESA. TFT: Abbreviation of thin film transistor, a type of LCD flat-panel display screen, in which each pixel is controlled by from one to four transistors. The TFT technology provides the best resolution of all the flat-panel techniques, but it is also the most expensive. TFT screens are sometimes called active-matrix LCDs. TI 34010: A video standard from Texas Instruments that supports a resolution of 1,024 by 768. TI 34010 conforms to TI's Graphics Architecture (TIGA). Unlike IBM's 8514/A, which supports the same resolution, TI 34010 is noninterlaced. TRUE COLOR: Refers to any graphics device or software that uses at least 24 bits to represent each dot or pixel. Using 24 bits means that more than 16 million unique colors can be represented. Since humans can only distinguish a few million colors, this is more than enough to accurately represent any color image. TOUCH SCREEN: A type of display screen that has a touch-sensitive transparent panel covering the screen. Instead of using a pointing device such as a mouse or light pen, you can use your finger to point directly to objects on the screen. Although touch screens provide a natural interface for computer novices, they are unsatisfactory for most applications because the finger is such a relatively large object. It is impossible to point accurately to small areas of the screen. In addition, most users find touch screens tiring to the arms after long use. TRUE COLOR: Refers to any graphics device or software that uses at least 24 bits to represent each dot or pixel. Using 24 bits means that more than 16 million unique colors can be represented. Since humans can only distinguish a few million colors, this is more than enough to accurately represent any color image. TTL MONITOR: TTL stands for transistor-transistor logic and refers to a special type of digital circuit. More commonly, however, TTL is used to designate any type of digital input or device. A TTL monitor, therefore, is a monitor that accepts digital input. TTL monitors are consistent with older graphics standards such as MDA, but all newer graphics standards, including VGA, require analog signals. Some monitors can accept both types of signal. VDT RADIATION: The radiation emitted by video display terminals. Like televisions, computer monitors emit various types of radiation. Since the late 1980s, there has been a public debate about whether this radiation poses a health problem. To date, however, there is no conclusive evidence to settle the question once and for all. VESA: Short for Video Electronics Standards Association, a consortium of video adapter and monitor manufacturers whose goal is to standardize video protocols. VESA has developed a family of video standards that offer greater resolution and more colors than VGA. These standards are known collectively as Super VGA (SVGA). VGA: Abbreviation of video graphics array, a graphics display system for PCs developed by IBM. VGA has become one of the de facto standards for PCs. In text mode, VGA systems provide a resolution of 720 by 400 pixels. In graphics mode, the resolution is either 640 by 480 (with 16 colors) or 320 by 200 (with 256 colors). The total palette of colors is 262,144. Unlike earlier graphics standards for PCs -- MDA, CGA, and EGA -- VGA uses analog signals rather than digital signals. Consequently, a monitor designed for one of the older standards will not be able to use VGA.Since its introduction in 1987, several other standards have been developed that offer greater resolution and more colors (see SVGA, 8514/A graphics standard, and XGA), but VGA remains the lowest common denominator. All PCs made today support VGA, and possibly some other more advanced standard. VIDEO ADAPTER: A board that plugs into a personal computer to give it display capabilities. The display capabilities of a computer, however, depend on both the logical circuitry (provided in the video adapter) and the display monitor. A monochrome monitor, for example, cannot display colors no matter how powerful the video adapter. Many different types of video adapters are available for PCs. Most conform to one of the video standards defined by IBM or VESA. Each adapter offers several different video modes. The two basic categories of video modes are text and graphics. In text mode, a monitor can display only ASCII characters. In graphics mode, a monitor can display any bit-mapped image. Within the text and graphics modes, some monitors also offer a choice of resolutions. At lower resolutions a monitor can display more colors. Most modern video adapters contain memory, so that the computer's RAM is not used for storing displays. In addition, some adapters have their own graphics coprocessor for performing graphics calculations. These adapters are often called graphics accelerators. Video adapters are also called video cards, video boards, and video display boards. VIDEO OVERLAY: The placement of a full-motion video window on the display screen. There are various techniques used to display video on a computer's screen, depending on whether the video source has been digitized or is still in analog NTSC format.Since computer monitors are generally analog, NTSC video can be merged with signals coming from the display adapter. Increasingly, faster computer buses (PCI, VL-bus, etc.) and faster video busses (Advanced Feature Connector, VM Channel, etc.), allow for analog video to be digitized and stored with other binary data for output. Then the display adapter turns it into analog scan lines for the monitor. VIDEO STANDARDS: There are a variety of video standards that define the resolution and colors for displays. Support for a graphics standard is determined both by the monitor and by the video adapter. The monitor must be able to show the resolution and colors defined by the standard, and the video adapter must be capable of transmitting the appropriate signals to the monitor. Listed here, in approximate order of increasing power and sophistication, are the more popular video standards for PCs. Note that many of these numbers represent only the minimums specified in the standards. Many suppliers of video adapters provide greater resolution and more colors. For more information, refer to the entries for the specific graphics systems. WRAM: Short for Window RAM, a type of RAM developed by Samsung Electronics that supports two ports. This enables a graphics adapter to fetch the contents of memory for display at the same time that new bytes are being pumped into memory. This results in much faster display than is possible with conventional single-port RAM.WRAM is similar to VRAM, but achieves even faster performance at less cost. XGA: Short for extended graphics array, a high-resolution graphics standard introduced by IBM in 1990. XGA was designed to replace the older 8514/A video standard. It provides the same resolutions (640 by 480 or 1024 by 768 pixels), but supports more simultaneous colors (65 thousand compared to 8514/A’s 256 colors). In addition, XGA allows monitors to be non-interlaced.