ANALOG - In the field of electronics, it refers to a signal that varies regularly and continuously over its range. Almost everything in the world can be described or represented in one of two forms: analog or digital. The principal feature of analog representations is that they are continuous. In contrast, digital representations consist of values measured at discrete intervals.

BITS - The smallest possible unit of information in any digital system expressed either as 0 or 1. (short for binary digit)

BYTES - A unit of binary information consisting of eight bits. One Byte represents one character or number.

CPU - Central Processing Unit is the central part of a computer. It includes circuitry (built around the CPU chip and mounted on the motherboard) that actually performs the computer's calculations, and the box in which that circuitry is housed.

DIGITAL - A process that can be represented in a discrete (non-continuous) form, such as numerical digits or integers. Digital watches are called digital because they go from one value to the next without displaying all intermediate values. Consequently, they can display only a finite number of times of the day. In contrast, watches with hands are analog, because the hands move continuously around the clock face. As the minute hand goes around, it not only touches the numbers 1 through 12, but also the infinite number of points in between.

GIGABYTES (GB) - A unit of measurement equal to 1,024 megabytes. Typically, a storage device capable of holding a gigabyte or more of information is a mass storage device such as a jaz disk, digital tape or large magneto-optical platters.

GUI - (Graphical user interface) An interface that translates computer codes into user-friendly graphic icons. Macintosh computers have always been utilizing such a system. Microsoft's similar interface for the DOS machines called Windows.

MEGABYTES (MB) - A unit of measurement equal to 1,024 kilobytes, or 1,048,576 bytes.

OPERATING SYSTEM - The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers. Examples are DOS, Mac OS X, Windows, UNIX and Linux.

PIXEL - Literally is a fusion of the words "pictorial elements." A screen pixel is the smallest area that a particular combination of software and hardware can illuminate on a monitor. Most contemporary monitors can display a maximum of 72 ppi (pixels per inch). A printer pixel is the smallest dot the printer can produce. Different printers have different dpi (dots per inch) capabilities. Generally the higher the dpi, the higher the image quality.

RAM - (random-access memory) The part of the computer's memory that stores information temporarily while it is being worked upon.

ROM - (read-only memory) Memory that can be read but not easily modified. Information remains in ROM permanently, even when the computerÍs power is off.

ANTI-ALIASING - An algorithm to smooth the appearance of the jagged lines "jaggies" created by the limited resolution of a graphic display system. Aliasing is caused by insufficient sampling of a digital signal.

BIT DEPTH - Graphics are often described by the number of bits used to represent each dot. A 1-bit image is monochrome; an 8-bit image supports 256 colors or grayscales; and a 24- or 32-bit graphic supports TRUE COLOR.

BITMAPPED or RASTER GRAPHICS - Refers to hardware and software that represent graphics images as bit maps. A representation, consisting of rows and columns of dots, of a graphics image in computer memory. The value of each dot (whether it is filled in or not) is stored in one or more bits of data. For simple monochrome images, one bit is sufficient to represent each dot, but for colors and shades of gray, each dot requires more than one bit of data. The more bits used to represent a dot, the more colors and shades of gray that can be represented. The density of the dots, known as the resolution, determines how sharply the image is represented. This is often expressed in dots per inch (dpi ) or simply by the number of rows and columns, such as 640 by 480. To display a bit-mapped image on a monitor or to print it on a printer, the computer translates the bit map into pixels (for display screens) or ink dots (for printers). Optical scanners and fax machines work by transforming text or pictures on paper into bit maps. Bit-mapped graphics are often referred to as raster graphics.

DPI - dots per inch. Typically used in reference to the resolution of a printer or digital file.

GAMMA - The measure of brightness (or darkness) of your computer monitor, as determined by its hardware. PCs have a darker screen presentation setting (2.2 gamma) than Macs (1.8 gamma).

LINE ART - A type of graphic consisting entirely of lines or large solid blocks, without any shading. Usually these are in vector graphics format.

LPI - lines per inch. Typically used in reference to the resolution of a half tone printer.

MOIRE PATTERN - An undesirable pattern in scanning and printing, resulting from incorrect screen angles or scanner descreening of overprinting halftones. Moire patterns can be minimized with the use of proper screen angles or descreening fliters when scanning.

MONITOR RESOLUTION - Monitor resolution is the amount of pixels per inch that can be displayed on your screen. Typically, 72 PPI. It is important to remember that if your image is set to screen resolution, 72 PPI, it will appear at actual size on the monitor. If your image is at 144 PPI, it will appear at twice its actual size in inches on the screen because only 72 of the 144 pixels can be displayed within one inch on the monitor.

OPTICAL RESOLUTION vs. INTERPOLATED RESOLUTION - The physical resolution at which a device can capture an image. The term is used most frequently in reference to optical scanners and digital cameras. In contrast, the interpolated resolution indicates the resolution that the device can yield through interpolation -- the process of generating intermediate values based on known values. For example, most scanners offer an optical resolution of 300 dpi, but an interpolated resolution of up to 4,800 dpi. This means that the scanner can actually capture 90,000 pixels per square inch. Then, based on the values of these pixels, it can add 15 additional pixels in-between each pair of known values to yield a higher resolution. NEVER TRUST INTERPOLATION! The input device is making something up from nothing - and often it is the detriment of the image.

PERIPHERAL DEVICE - A piece of hardware - such as a monitor, scanner, printer, or modem- used in conjunction with a computer and under the computer's control.

PPI - pixels per inch. Typically used in reference to the resolution of a computer monitor or a digital image file on screen.

RESAMPLING - To change the resolution of an image. Resampling down discards pixel information in an image; resampling up adds pixel information through interpolation.

RESOLUTION - (Spatial Resolution or Spatial Relations) The number of pixels per inch in an image or the number of dots per inch used by an output device. Resolution can also refer to the number of bits per pixel. Image resolution, or DPI (dots per inch), refers to the spacing of pixels in an image. If an image has 72 dpi, this means it has 5184 pixels in a square inch because 72 x 72 = 5184. The higher the resolution, the more pixels in an image. For example, a 3x3 image at 72 dpi has 46,656 one inch square blocks of information. The same image with 300 DPI has 810,000 one inch square blocks of information.

RGB IMAGE - A three-channel image containing a red, green, and blue channel.

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.

VECTOR GRAPHICS - The other (aside from raster graphics) method for representing images is known as vector graphics or object-oriented graphics. With vector graphics, images are represented as mathematical formulas that define all the shapes in the image. Vector graphics are more flexible than bit-mapped graphics because they look the same even when you scale or stretch them to different sizes. In addition, images stored as vectors look better on devices (monitors and printers) with higher resolution, whereas bit-mapped images always appear the same regardless of a device's resolution. Another advantage of vector graphics is that representations of images often require less memory than bit-mapped images do. In contrast, bit-mapped graphics become ragged when you shrink or enlarge them. Fonts represented with vector graphics are called scalable fonts , outline fonts , or vector fonts. The best-known example of a vector font system is PostScript. Bit-mapped fonts, also called raster fonts, must be designed for a specific device and a specific size and resolution. Note that most output devices, including dot-matrix printers, laser printers, and display monitors, are raster devices (plotters are the notable exception). This means that all objects, even vector objects, must be translated into bit maps before being output. The difference between vector graphics and raster graphics, therefore, is that vector graphics are not translated into bit maps until the last possible moment, after all sizes and resolutions have been specified. PostScript printers, for example, have a raster image processor (RIP) that performs the translation within the printer. In their vector form, therefore, graphics representations can potentially be output on any device, with any resolution, and at any size.

ADDITIVE PRIMARY COLORS (RGB) Red, green and blue are the three colors used to create all other colors when direct or transmitted light is used (for example, on a computer monitor). They are called additive primaries, because when pure red, green, and blue are superimposed on one another, they create white.

HUE - The main attribute of a color that distinguishes it from other colors. Red, blue, green, yellow, etc. are hues. White, black and gray are not considered hues

PROCESS COLORS (CMYK) The four color pigments-cyan, magenta, yellow, and black-used in color printing.