Vocab of Graphic and Computer related terms

COMPUTER GRAPHICS and DESKTOP PUBLISHING TERMS AND CONCEPTS

1. Desktop publishing
Using a personal computer or workstation to produce high-quality printed documents. A desktop publishing system allows you to use different typefaces, specify various margins and justifications, and embed illustrations and graphs directly into the text. The most powerful desktop publishing systems enable you to create illustrations, while less powerful systems let you insert illustrations created by other programs. As word-processing programs become more and more powerful, the line separating such programs from desktop publishing systems is becoming blurred. In general, though, desktop publishing applications give you more control over typographical characteristics, such as kerning, and provide more support for full-color output.

A particularly important feature of desktop publishing systems is that they enable you to see on the display screen exactly how the document will appear when printed. Systems that support this feature are called WYSIWYGs (what you see is what you get). Until recently, hardware costs made desktop publishing systems impractical for most uses. But as the prices of personal computers and printers have fallen, desktop publishing systems have become increasingly popular for producing newsletters, brochures, books, and other documents that formerly required a typesetter.

Once you have produced a document with a desktop publishing system, you can output it directly to a printer or you can produce a PostScript file which you can then take to a service bureau. The service bureau has special machines that convert the PostScript file to film, which can then be used to make plates for offset printing. Offset printing produces higher-quality documents, especially if color is used, but is generally more expensive than laser printing.

2. Graphic(s)
Pertains to any computer device or program that makes a computer capable of displaying and manipulating pictures. For example, laser printers and plotters are graphics devices because they permit the computer to output pictures. A graphics monitor is a display monitor that can display pictures. A graphics board (or graphics card) is a printed circuit board that, when installed in a computer, permits the computer to display pictures. Many software applications include graphics components.

Such programs are said to support graphics. For example, certain word processors support graphics because they let you draw or import pictures. All CAD/CAM systems support graphics. Some database management systems and spreadsheet programs support graphics because they let you display data in the form of graphs and charts. Such applications are often referred to as business graphics.

The following are also considered graphics applications :

paint programs : Allow you to create rough freehand drawings. The images are stored as bit maps and can easily be edited. (Adobe Photoshop, Painter)
illustration/design programs: Supports more advanced features than paint programs, particularly for drawing curved lines. The images are usually stored in vector -based formats. Illustration/design programs are often called draw programs. (Adobe Illustrator, Freehand)
presentation graphics software : Lets you create bar charts, pie charts, graphics, and other types of images for slide shows and reports. The charts can be based on data imported from spreadsheet applications.
animation software: Enables you to chain and sequence a series of images to simulate movement. Each image is like a frame in a movie.
CAD software: Enables architects and engineers to draft designs.
desktop publishing : Provides a full set of word-processing features as well as fine control over placement of text and graphics, so that you can create newsletters, advertisements, books, and other types of documents.

In general, applications that support graphics require a powerful CPU and a large amount of memory. Many graphics applications -- for example, computer animation systems -- require more computing power than is available on personal computers and will run only on powerful workstations or specially designed graphics computers. This is true of all three-dimensional computer graphics applications. In addition to the CPU and memory, graphics software requires a graphics monitor and support for one of the many graphics standards. Most PC programs, for instance, require VGA graphics. If your computer does not have built-in support for a specific graphics system, you can insert a video adapter card. The quality of most graphics devices is determined by their resolution -- how many points per square inch they can represent -- and their color capabilities.

3. Vector
Same as object-oriented graphics, refers to software and hardware that use geometrical formulas to represent images. The other method for representing graphical images is through bit maps, in which the image is composed of a pattern of dots. This is sometimes called raster graphics. Programs that enable you to create and manipulate vector graphics are called draw programs, whereas programs that manipulated bit-mapped images are called paint programs.

Vector-oriented images are more flexible than bit maps because they can be resized and stretched. 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. Almost all sophisticated graphics systems, including CADD systems and animation software, use vector graphics. In addition, many printers (PostScript printers, for example) use vector graphics. Fonts represented as vectors are called vector fonts, scalable fonts, object-oriented fonts, and outline fonts. 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.

4. Raster (bitmapped graphics or paint programs, ex. Photoshop)
A graphics program that enables you to draw pictures on the display screen which are represented as bit maps (bit-mapped graphics). In contrast, draw programs use vector graphics (object-oriented images), which scale better. Most paint programs provide the tools shown below in the form of icons. By selecting an icon, you can perform functions associated with the tool. In addition to these tools, paint programs also provide easy ways to draw common shapes such as straight lines, rectangles, circles, and ovals. Sophisticated paint applications are often called image editing programs. These applications support many of the features of draw programs, such as the ability to work with objects. Each object, however, is represented as a bit map rather than as a vector image.

5. Bitmap
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. The other 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 them to different sizes. 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.

6. 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 screen 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.

7. Dpi
Abbreviation of dots per inch, which indicates the resolution of images. The more dots per inch, the higher the resolution. A common resolution for laser printers is 600 dots per inch. This means 600 dots across and 600 dots down, so there are 360,000 dots per square inch.

Printers:

1) Laser
A type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work. Because an entire page is transmitted to a drum before the toner is applied, laser printers are sometimes called page printers. There are two other types of page printers that fall under the category of laser printers even though they do not use lasers at all.

One uses an array of LEDs to expose the drum, and the other uses LCDs. Once the drum is charged, however, they both operate like a real laser printer. One of the chief characteristics of laser printers is their resolution -- how many dots per inch (dpi) they lay down. The available resolutions range from 300 dpi at the low end to 1,200 dpi at the high end. By comparison, offset printing usually prints at 1,200 or 2,400 dpi. Some laser printers achieve higher resolutions with special techniques known generally as resolution enhancement. In addition to the standard monochrome laser printer, which uses a single toner, there also exist color laser printers that use four toners to print in full color.

Color laser printers tend to be about five to ten times as expensive as their monochrome siblings. Laser printers produce very high-quality print and are capable of printing an almost unlimited variety of fonts. Most laser printers come with a basic set of fonts, called internal or resident fonts, but you can add additional fonts in one of two ways:

font cartridges : Laser printers have slots in which you can insert font cartridges, ROM boards on which fonts have been recorded. The advantage of font cartridges is that they use none of the printer's memory.

soft fonts : All laser printers come with a certain amount of RAM memory, and you can usually increase the amount of memory by adding memory boards in the printer's expansion slots. You can then copy fonts from a disk to the printer's RAM. This is called downloading fonts. A font that has been downloaded is often referred to as a soft font, to distinguish it from the hard fonts available on font cartridges. The more RAM a printer has, the more fonts that can be downloaded at one time. In addition to text, laser printers are very adept at printing graphics. However, you need significant amounts of memory in the printer to print high-resolution graphics. To print a full-page graphic at 300 dpi, for example, you need at least 1 MB (megabyte) of printer RAM. For a 600-dpi graphic, you need at least 4 MB RAM. Because laser printers are nonimpact printers, they are much quieter than dot-matrix or daisy-wheel printers. They are also relatively fast, although not as fast as some dot-matrix printers. The speed of laser printers ranges from about 4 to 20 pages of text per minute (ppm). A typical rate of 6 ppm is equivalent to about 40 characters per second (cps). Laser printers are controlled through page description languages (PDLs).

There are two de facto standards for PDLs:

PCL : Hewlett-Packard (HP) was one of the pioneers of laser printers and has developed a Printer Control Language (PCL) to control output. There are several versions of PCL, so a printer may be compatible with one but not another. In addition, many printers that claim compatibility cannot accept HP font cartridges.

PostScript : This is the de facto standard for Apple Macintosh printers and for all desktop publishing systems.
Most software can print using either of these PDLs. PostScript tends to be a bit more expensive, but it has some features that PCL lacks and it is the standard for desktop publishing. Some printers support both PCL and PostScript.

2) Offset printing
A printing technique whereby ink is spread on a metal plate with etched images, then transferred to an intermediary surface such as a rubber blanket, and finally applied to paper by pressing the paper against the intermediary surface. Most print shops use offset printing to produce large volumes of high-quality documents. Although the equipment and set-up costs are relatively high, the actual printing process is relatively inexpensive.

Desktop publishing generally involves producing documents on the computer, printing out drafts on a laser printer, and then offset printing the final version. To produce the plates used in offset printing, a print shop requires either film or high-resolution paper output, which the printer can then photograph. You can obtain either by taking a PostScript file to a service bureau.

8. Higher resolution
A collection of techniques used in many laser printers to enable the printer to print at a higher resolution than normal. Most laser printers have printer engines that print at either 300 dpi (dots per inch) or 600 dpi. Using clever algorithms that recognize curved lines, a printer with resolution enhancement can produce output whose resolution appears to be much higher than the print engine's rated resolution.

This is why many printer manufacturers characterize their printers with two resolution ratings: the engine resolution and the effective resolution. A common resolution enhancement technique is to vary the size of the dots.

9. Monitor (color, etc.)
A display monitor capable of displaying many colors. In contrast, a monochrome monitor can display only two colors -- one for the background and one for the foreground. Color monitors implement the RGB color model by using three different phosphors that appear red, green, and blue when activated.

By placing the phosphors directly next to each other, and activating them with different intensities, color monitors can create an unlimited number of colors. In practice, however, the real number of colors that any monitor can display is controlled by the video adapter. Color monitors based on CRT technology employ three different techniques to merge phosphor triplets into pixels:

Dot-trio shadow masks place a thin sheet of perforated metal in front of the screen. Since electrons can pass only through the holes in the sheet, each hole represents a single pixel.
Aperture-grille CRTs place a grid of wires between the screen and the electron guns.
Slot-mask CRTs uses a shadow mask but the holes are long and thin. It's sort of a cross between the dot-trio shadow mask and aperture-grill techniques.

10. Byte
Abbreviation for binary term, a unit of storage capable of holding a single character. On almost all modern computers, a byte is equal to 8 bits. Large amounts of memory are indicated in terms of kilobytes (1,024 bytes), megabytes (1,048,576 bytes), and gigabytes (1,073,741,824 bytes). A disk that can hold 1.44 megabytes, for example, is capable of storing approximately 1.4 million characters, or about 3,000 pages of information.

11. Kilobyte
In decimal systems, kilo stands for 1,000, but in binary systems, a kilo is 1,024 (2 to the 10th power). Technically, therefore, a kilobyte is 1,024 bytes, but it is often used loosely as a synonym for 1,000 bytes. For example, a computer that has 256K main memory can store approximately 256,000 bytes (or characters) in memory at one time. A megabyte is 2 to the 20th power (approximately 1 million) and a gigabyte is 2 to the 30th power (approximately 1 billion). In computer literature, kilobyte is usually abbreviated as K or Kb. To distinguish between a decimal K (1,000) and a binary K (1,024), the IEEE has suggested following the convention of using a small k for a decimal kilo and a capital K for a binary kilo, but this convention is by no means strictly followed.

12. Megabyte
(1) When used to describe data storage, 1,048,576 (2 to the 20th power) bytes. Megabyte is frequently abbreviated as M or MB. (2) When used to describe data transfer rates, as in MBps, it refers to one million bytes.

13. Gigabyte

2 to the 30th power (1,073,741,824) bytes. One gigabyte is equal to 1,024 megabytes. Gigabyte is often abbreviated as G or GB

14. Disk
A round plate on which data can be encoded. There are two basic types of disks: magnetic disks and optical disks. On magnetic disks, data is encoded as microscopic magnetized needles on the disk's surface. You can record and erase data on a magnetic disk any number of times, just as you can with a cassette tape. Magnetic disks come in a number of different forms:

floppy disk : A typical 5¼-inch floppy disk can hold 360K or 1.2MB (megabytes). 3½-inch floppies normally store 720K, 1.2MB or 1.44MB of data.
hard disk : Hard disks can store anywhere from 20MB to more than 10GB. Hard disks are also from 10 to 100 times faster than floppy disks.
removable cartridge : Removable cartridges are hard disks encased in a metal or plastic cartridge, so you can remove them just like a floppy disk. Removable cartridges are very fast, though usually not as fast as fixed hard disks.
Optical disks record data by burning microscopic holes in the surface of the disk with a laser. To read the disk, another laser beam shines on the disk and detects the holes by changes in the reflection pattern.

Optical disks come in three basic forms:

CD-ROM : Most optical disks are read-only. When you purchase them, they are already filled with data. You can read the data from a CD-ROM, but you cannot modify, delete, or write new data.
WORM : Stands for write-once, read-many. WORM disks can be written on once and then read any number of times; however, you need a special WORM disk drive to write data onto a WORM disk.
erasable optical (EO ): EO disks can be read to, written to, and erased just like magnetic disks.
The machine that spins a disk is called a disk drive. Within each disk drive is one or more heads (often called read/write heads) that actually read and write data. Accessing data from a disk is not as fast as accessing data from main memory, but disks are much cheaper. And unlike RAM, disks hold on to data even when the computer is turned off. Consequently, disks are the storage medium of choice for most types of data. Another storage medium is magnetic tape. But tapes are used only for backup and archiving because they are sequential-access devices (to access data in the middle of a tape, the tape drive must pass through all the preceding data).
A new disk, called a blank disk, has no data on it. Before you can store data on a blank disk, however, you must format it

15. Format
(v) (1) To prepare a storage medium, usually a disk, for reading and writing. When you format a disk, the operating system erases all bookkeeping information on the disk, tests the disk to make sure all sectors are reliable, marks bad sectors (that is, those that are scratched), and creates internal address tables that it later uses to locate information. You must format a disk before you can use it. Note that reformatting a disk does not erase the data on the disk, only the address tables. Do not panic, therefore, if you accidentally reformat a disk that has useful data.

A computer specialist should be able to recover most, if not all, of the information on the disk. You can also buy programs that enable you to recover a disk yourself. The previous discussion, however, applies only to high-level formats, the type of formats that most users execute. In addition, hard disks have a low-level format, which sets certain properties of the disk such as the interleave factor. The low-level format also determines what type of disk controller can access the disk (e.g., RLL or MFM). Almost all hard disks that you purchase have already had a low-level format. It is not necessary, therefore, to perform a low-level format yourself unless you want to change the interleave factor or make the disk accessible by a different type of disk controller.

Performing a low-level format erases all data on the disk. (2) To specify the properties, particularly visible properties, of an object. For example, word processing applications allow you to format text, which involves specifying the font, alignment, margins, and other properties. (n) A particular arrangement. Almost everything associated with computers has a format.

16. Memory
Internal storage areas in the computer. The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk.

Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information.

There are several different types of memory:

RAM (random-access memory): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost.
ROM (read-only memory): Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to.
PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile.
EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light.
EEPROM (electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge.

17. Mass Storage
Refers to various techniques and devices for storing large amounts of data. The earliest storage devices were punched paper cards, which were used as early as 1804 to control silk-weaving looms. Modern mass storage devices include all types of disk drives and tape drives. Mass storage is distinct from memory, which refers to temporary storage areas within the computer. Unlike main memory, mass storage devices retain data even when the computer is turned off.

The main types of mass storage are:

floppy disks : Relatively slow and have a small capacity, but they are portable, inexpensive, and universal.
hard disks : Very fast and with more capacity than floppy disks, but also more expensive. Some hard disk systems are portable (removable cartridges), but most are not.
optical disks : Unlike floppy and hard disks, which use electromagnetism to encode data, optical disk systems use a laser to read and write data. Optical disks have very large storage capacity, but they are not as fast as hard disks. In addition, the inexpensive optical disk drives are read-only. Read/write varieties are expensive.
tapes : Relatively inexpensive and can have very large storage capacities, but they do not permit random access of data.
Mass storage is measured in kilobytes (1,024 bytes), megabytes (1,024 kilobytes), gigabytes (1,024 megabytes) and terabytes (1,024 gigabytes).
Mass storage is sometimes called auxiliary storage.

18. Zip disk (drive)
A high-capacity floppy disk drive developed by Iomega Corporation. Zip disks are slightly larger than conventional floppy disks, and about twice as thick. They can hold 100 or 250 MB of data. Because they're relatively inexpensive and durable, they have become a popular media for backing up hard disks and for transporting large files.

19. Backup
(n) To copy files to a second medium (a disk or tape) as a precaution in case the first medium fails. One of the cardinal rules in using computers is, Back up your files regularly. This is critical!! Even the most reliable computer is apt to break down eventually. Many professionals recommend that you make two, or even three, backups of all your files. To be especially safe, you should keep one backup in a different location from the others. You can back up files using operating system commands, or you can buy a special-purpose backup utility. Backup programs often compress the data so that backups require fewer disks; (v) (1) The act of backing up. (2) A substitute or alternative. The term backup usually refers to a disk or tape that contains a copy of data.

20. Data compression
Storing data in a format that requires less space than usual. Data compression is particularly useful in communications because it enables devices to transmit the same amount of data in fewer bits. There are a variety of data compression techniques, but only a few have been standardized. The CCITT has defined a standard data compression technique for transmitting faxes (Group 3 standard) and a compression standard for data communications through modems (CCITT V.42bis). In addition, there are file compression formats, such as ARC and ZIP.
Data compression is also widely used in backup utilities, spreadsheet applications, and database management systems. Certain types of data, such as bit-mapped graphics, can be compressed to a small fraction of their normal size.

21. Peripheral device
A computer device, such as a CD-ROM drive or printer, that is not part of the essential computer, i.e., the memory and microprocessor. Peripheral devices can be external -- such as a mouse, keyboard, printer, monitor, external Zip drive or scanner -- or internal, such as a CD-ROM drive, CD-R drive or internal modem. Internal peripheral devices are often referred to as integrated peripherals. Also see I/O.

22. Scanner
A device that can read text or illustrations printed on paper and translate the information into a form the computer can use. A scanner works by digitizing an image -- dividing it into a grid of boxes and representing each box with either a zero or a one, depending on whether the box is filled in. (For color and gray scaling, the same principle applies, but each box is then represented by up to 24 bits.) The resulting matrix of bits, called a bit map, can then be stored in a file, displayed on a screen, and manipulated by programs. Optical scanners do not distinguish text from illustrations; they represent all images as bit maps. Therefore, you cannot directly edit text that has been scanned. To edit text read by an optical scanner, you need an optical character recognition (OCR ) system to translate the image into ASCII characters. Most optical scanners sold today come with OCR packages.

Scanners differ from one another in the following respects:
· scanning technology: Most scanners use charge-coupled device (CCD) arrays, which consist of tightly packed rows of light receptors that can detect variations in light intensity and frequency. The quality of the CCD array is probably the single most important factor affecting the quality of the scanner. Industry-strength drum scanners use a different technology that relies on a photomultiplier tube (PMT), but this type of scanner is much more expensive than the more common CCD -based scanners.

resolution: The denser the bit map, the higher the resolution. Typically, scanners support resolutions of from 72 to 600 dpi.
bit depth: The number of bits used to represent each pixel. The greater the bit depth, the more colors or grayscales can be represented. For example, a 24-bit color scanner can represent 2 to the 24th power (16.7 million) colors. Note, however, that a large color range is useless if the CCD arrays are capable of detecting only a small number of distinct colors.

Some scanners are small hand-held devices that you move across the paper. These hand-held scanners are often called half-page scanners because they can only scan 2 to 5 inches at a time. Hand-held scanners are adequate for small pictures and photos, but they are difficult to use if you need to scan an entire page of text or graphics. Larger scanners include machines into which you can feed sheets of paper. These are called sheet-fed scanners. Sheet-fed scanners are excellent for loose sheets of paper, but they are unable to handle bound documents. A second type of large scanner, called a flatbed scanner, is like a photocopy machine. It consists of a board on which you lay books, magazines, and other documents that you want to scan. Overhead scanners (also called copyboard scanners) look somewhat like overhead projectors. You place documents face-up on a scanning bed, and a small overhead tower moves across the page.

These selected terms and more are available online. Please also see http://www.webopedia.com for more computer and graphic related terms.