Selection criteria for graphics hardware

Selection criteria for graphics hardware

Comput & Graphics Vol. 8, No. 3, pp. 295-301, 1984 0097-8493184 $3.00 + .00 Pergamon Press Ltd. Printed in the U.S.A. Glossary SELECTION CRITERIA ...

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Comput & Graphics Vol. 8, No. 3, pp. 295-301, 1984

0097-8493184 $3.00 + .00 Pergamon Press Ltd.

Printed in the U.S.A.

Glossary

SELECTION CRITERIA FOR GRAPHICS HARDWARES HENK DE GROOT Tektronix, Inc., Wiisonville, Oregon, U.S.A.

Abstract--Engineering design and drafting applications currently account for the largest number of computer graphics applications; however, experts predict that the growth of business graphics applications will exceed all others in the industry. Selection criteria for the various graphics hardware components commonly used in business environments---displays, terminals, hardcopy devices, input devices and storage media--will be discussed, with an emphasis on technology trends. The marketplace is crowded with graphics hardware devices, and technology continues to bound ahead at an uncanny pace. Guidelines for selecting the appropriate equipment are generally useful, especially if you are a businessman just entering the world of business graphics. There are a number of components to consider and many options for each. The major areas of consideration will be: displays, terminals, hardcopy devices, input devices, and storage media. TRENDS SHAPING THE MARKETPLACE

Graphics equipment purchases for business applications may soon surpass those for engineering and scientific applications, which pioneered the development of computer graphics. MIS (Management Information Systems) applications for graphics are estimated to have a growth rate of 50% a year. To accommodate this burgeoning community of users, manufacturers have made features such as ease of use, color, high resolution and affordability the top design priorities. Several distinct trends have shaped the graphics hardware marketplace over the last five years:

0 Increasing business applications. Graphics is proving to be a boon to corporate decision-making. Graphic images reduce voluminous quantities of data to simple pictorial form, enabling managers to instantly spot irregularities in data without leafing through pages of printout. Typical business applications include plotting trends in sales and product performance, employee statistics, company earnings, and countless other business data.

tions move from the engineering laboratories to the office, the technical sophistication of users drops dramatically. Vendors are forced to bury all complex graphics commands, making the user interface as simple and easy-to-understand as possible. An increased concern with good ergonomic design parallels the demand for user-friendliness.

0 Migration to micros. With the growing use ofpersonal computers at home and at work, there is an increasing demand for graphics packages which support these devices. Sophisticated graphics functionality is no longer the sole province of mainframe computers. 0 Vendors offering systems solutions. Vendors which once dealt exclusively in system components---e.g. plotters or terminals--are now expanding their product lines to offer total graphics systems to their customers. THE GRAPHICS WORKSTATION

A graphics workstation for MIS consists of the complete set of input, output, display and storage devices needed to handle a graphics application. With the variety of devices and technologies required to implement graphics, choices are complex. Typical workstation hardware elements include:

0 Displays and terminals, on which to design and view work.

0 Hardcopy devices, such as copiers and plotters.

0 Greater sophistication in CAD/CAM. Computeraided design and manufacturing continue to be primary applications for computer graphics, and CAD/CAM engineers are demanding greater sophistication in their tools. The business community will benefit from advances designed to serve the engineering community.

0 Input devices, such as joysticks, digitizers and lightpens.

0 Mass storage milts required for the large memory demands of graphics images.

0 Costs are dropping at an amazing rate. Sophisticated graphics terminals are available today for under $5000. 0 Increasing user-friendliness. As graphics applica$ This article was first pre~ntcd at the CAMP83 Conference in Berlin, West Germany, March 1983.

A variety of technologies are available for each of these devices, all with different performance characteristics and cost trade offs. An understanding of major technologies available and indications of new developments can assist in successful selection.

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DISPLAYSAND TERMINALS Available display technologies The display, or screen, of a terminal is usually a cathode ray tube (CRT), though new technologies are making inroads on this traditional display medium. There are three technologies to choose from, depending on the requirements for resolution, interactivity, color capabilities, area-fill capabilities, and cost. The primary CRT display technologies are raster scan, vector refresh and storage. Raster scan monitors produce images with a matrix of picture-elements called pixels. The electron beam is swept across a phosphor-coated screen line by line, illuminating pixels according to an image pattern stored in memory. A primary characteristic of raster scan monitors is the wide range of available colors. They also have the ability to display gray scale for shading and modeling. They offer high contrast, brightness and dynamics at a relatively low cost. Raster displays are the most effective for MIS applications, due to their ability to offer many colors, their good area-fill capabilities (used to shade business graphics such as bar and pie charts) and their interactivity. One problem with raster technology involves potentially poor image quality caused by the stair-step representation of the pixels on diagonal lines. One way to reduce the jagged effect is to improve resolution by increasing the number of pixels on the screen, but this increases memory requirements and thus price. An alternative method of minimizing the impact of jagged lines is to blur them using anti-aliasing techniques. Vector refresh is another CRT display technology. Vector refresh tubes draw images directly onto the phosphor-coated screen in a smooth, continuous stroke which must be constantly refreshed. The chief advantages of vector refresh tubes are high resolution and the ability to display motion. Images can also be edited before storage. Limited color capabilities are available. A disadvantage is the fact that vector refresh displays evidence screen flicker when complex images are presented. This is usually unacceptable in business applications. Also making vector refresh a poor choice for business applications are poor area-fill and a high cost due to cosily electronics necessary to drive the refresh mechanism. Vector refresh displays are best utilized in engineering and scientific apphcatious, such as complex geometric modeling, finite-element analysis, kinematic modeling and analysis, and motion simulation. The storage tube is widely used in engineering environments. It is relatively low in cost, compared to refresh technologies, although it does have disadvantages. The storage tube has limited color, low brightness and is poor at area-fill. In the storage tube, the writing beam traces out an image directly onto the screen, where it is stored by the phosphor without need for refresh or peripheral memory. Because there is no refresh, there is no flicker. The storage tube is thus the best vehicle for

conveying large amounts of high-resolution graphic data, such as integrated circuit design. The degree of resolution is excellent, and cost can be very low for some models. Display, terminal selection criteria Selection criteria for graphics displays include: © © © O ©

resolution interactivity color area-fill cost

Resolution. Resolution is the result of a combination of factors: number of lines on the screen, refresh rate, contrast ratio, convergence of the color writing beams, spot size or line width, and anti-aliasing techniques. In essence, resolution refers to the smallest or finest displayable detail; thus, the resolution requirements for a workstation depend on the application. Too many or too few lines result in poor resolution. The appropriate line number depends upon spot profile and spot size. Spot profile is a measure of the energy distribution in each spot on the screen. Too many lines on a screen with a large spot or poor profile will negatively affect the resolution. Refresh rate is the rate at which the lines on the display are refreshed or redrawn. The normal 30 Hz (30 redraws per second) is perceptible to the human eye as flicker and can cause visual fatigue. Some newer terminals refresh at 60 Hz, which substantially reduces flicker. An interlaced display is one in which the screen fines are refreshed alternately--every other line on every other cycle. Non-interlaced displays refresh every line on every refresh cycle and result in less flicker. The contrast refers to the brightness and/or color difference between foreground and background colors on the screen. Too low or high a contrast between screen colors will result in poor resolution. Convergence is the intersection of the red, green and blue color beams which comprise a raster drawing beam. Misconvergence, a condition common to all color displays, occurs when the beams do not intersect correctly. Misconvergence can cause poor color, fuzziness, visual fatigue and even loss of graphics information. Anti-aliasing, a software technique used to smooth the jagged lines sometimes found in raster displays, is accomplished by defocusing the beam so that separate pixels appear to blend into one fine. Anti-aliasing can have a negative effect on resolution, since, by definition, it blurs the lines; but, it has a positive effect on image quality. Most manufacturers are working to improve resolution quality for raster tubes; however, high resolution is expensive. It should be kept in mind that not all graphics applications need high resolution. In fact, for many MIS applications, only moderate resolution is required.

Sel~fioncriteria ~r graphics hardware

Interactivity. Display interactivity,: sometimes called dynamics, is the ease with which a user can alter a graphic image. Raster and vector refresh technologies are highly dynamic and allow unlimited manipulation of an image. Storage technology, on the other hand, offers interaetivity via a refresh capability which allows the image to be altered until it is stored in display memory. After storage, the image may be altered in less than one half of a second with a fast redraw technique. However, for applications requiring a great deal of complex dynamics or animations, raster technology is probably best. Color. Color is a significant display enhancement for many graphics applications. Color terminals tend to be preferred by many users, both because of cultural and personal preference and because of real productivity gains. Color is useful in locating organizing, and drawing attention to (and away from) information. Color can also be used to show relationships of degree, such as coding temperatures to correspond with real-life color changes, perhaps from white hot to ice blue. Color, like resolution, is not always necessary in a graphics application. Color displays are generally costlier than monochrome. Area-fill capability. This is the measure of how well the display can shade geometric areas with solid color. Only raster displays do this well. Business graphics in particular tend to depend on good areafill capabilities. Cost. A clear relationship exists between the levels of display performance and cost. The user must carefully weigh the benefits of each display attribute for his or her specific application. Additional terminal considerations Terminal-related variables which are not directly related to the display can make a difference in some application areas. These include terminal ergonomics, data communications capabilities, and level of intelligence. Ergonomics. Display ergonomics deals with the viewability of the display; i.e. image quality, and the degree to which the display causes eye fatigue or enhances productivity. Obviously, viewability depends on all of the factors discussed above, such as resolution and color. Ergonomic features of the physical terminal itself include keyboard detachability and terminal moveability, i.e. ability to swivel to meet user eye-level, both imlxmant for user comfort. Important to work flow is the presence of soft, or programmable, keys. Softkeys are those which can be programmed to perform functions that are used frequently or to abbreviate a string of commands. Softkeys make it easier for the novice user to enter commands, while reducing the chance for erroneous input. Expert users appreciate softkeys for the time saved in instruction

entry. Some graphics terminals also have special function keys that rapidly move the cursor from one part of the drawing to another or take you to a "home base."

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Such function keys greatly facilitate the rapid input of graphics data. Again, the ergonomic needs will depend on the intended application. Communications. As data communications standards become more widely accepted and effective communications networks more widely available, compatibility with these standards and networks will become a significant consideration in purchasing decisions. Large organizations with distributed processing and many independent workstations should acquire hardware components that are compatible with dissimilar components and have the ability to grow with applications. For instance, some graphics terminals available today have standardized graphics and interfacing capabilities, enabling applications to grow from monochrome to high-resolution to full color, with minimal software changes. Compatibility can protect the customer's software investment, which is often greater than his investment in hardware. Intelligence. Level of terminal intelligence is also an important consideration. A host-dq~endent terminal can be dedicated to a specific task and can be modified for others only through hardware changes. They are usually the lowest in cost and are suited to applications requiring simple output graphs prepared by the host computer. A smart terminal is microprocessor-based and may be programmed to accept changes through software. Smart terminals usually have softkeys. A smart terminal can be used for the same applications as a host-dependent terminal but is easier for the novice user to operate. An intelligent terminal possesses not only the microprocessor-based programmability of a smart terminal but contains a CPU for local data processing. Intelligent terminals often have local storage capabilities, making them fairly independent from the host mainframe and allowing their use as stand-alone computers. The intelligent terminal offers the greatest user interactivity, as everything the user needs for graphics applications is right at his fingertips: graphics software, display facilities, processing and storage. There is no need to transfer graphics instructions or source data back and forth from the host mainframe to the graphics workstation. Response time is immediate, and not to be forgotten are the cost benefits gained from off-loading the host. Intelligent terminals are ideal for expert users who will be performing complex graphics tasks, but they offer more than is required for many graphics applications. Since their cost is much greater than those for smart or host-dependent terminals, intelligent terminals should be carefully matched to applications that require their considerable capabilities. Every feature costs money, and not all features are necessary for all applications. Terminals with more intelligence, interactivity, resolution or color will increase the cost accordingly, but very few applica-

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tions require all of these features. Judicious evaluation of application needs before purchasing can result in considerable savings.

Future display technologies Significant improvements have taken place in raster technology, primarily because of developments in industries outside of computer graphics. Recent improvements in refresh rates and pixel storage have resulted in significant improvements in luminance and resolution. Lower costs are the results of reductions in the price of computer memory (raster tubes store images in memory). The tremendous growth and development of graphics technologies means constant change in system capabilities. Resolution limits and color performance represent two areas of rapid change. New technologies, such as electroluminescence, plasma and liquid crystal, are capable of overcoming some limitations of current technologies, but the degree to which they can solve specific problems in particular applications remains to be seen. HARDCOPY DEVICES

Hardcopy technologies There is a growing consensus that hardcopy devices will soon attain a higher profile than terminals in the realm of graphics equipment, due to the fact that it is the hardcopy device that provides the ultimate decision or action documents to users. Several equipment types dominate the hardcopy arena today" pen plotters, printer plotters, CRT copiers, ink-jet printers, impact printers and camera systems. Pen plotters are electromechanical devices which produce plots with a motor-driven pen. Plotters come in a variety of sizes with a variety of pen types and line quality. Depending on the software driving them, pen plotters can be used to copy a CRT image, to plot independently of the CRT image, or to create an even higher resolution plot of the same data being displayed by the CRT (provided high resolution data is available). The cost of pen plotters is dropping daily, and already they are some of the most inexpensive graphics output devices available. Line quality and resolution are excellent, and a variety of surface media is available, including transparent film (used for making overhead transparencies). Due to their mechanical nature, plotters can be relatively slow for complex images. Also, because plotters are basically vector devices, they perform poorly in applications requiring area-fill, such as solidcolored bar or pie charts. Despite the drawbacks, plotters are among the most popular hardcopy devices for business graphics. Work is continuing on increasing speed, improving resolution and area-fill capabilities and reducing costs. Printer plotters copy the CRT image and produce images electrostatically, meaning that electrodes placed on charged paper are "developed" when they

pass through a toner. Printer plotters offer high speed and excellent black and white image quality. Color electrostatic devices have also been announced recently. Printer plotter costs run high, and their size often makes them cumbersome to operate. The toner often causes problems, as well, and printer plotters are limited in the surface media they are capable of printing on (no transparent film). CRTcopiers also copy the CRT image, usually with an electrophotographic technique, whereby light beams draw an image on light-sensitive paper, which is then developed photographically. Device cost and cost per copy are relatively low for copiers, print speed is high, and the equipment is compact and easy to use. Copier research and development, as that for plotters, is making rapid strides. The future should see continued advances towards improved image quality, lower costs and greater userfriendfiness. Ink-jet printers are an emerging technology which offer fine resolution, excellent area-fill capabilities and higher speed than pen plotters. Using one of two basic ink-jet technologies, ink-jet printers create images by spraying fine streams of colored ink onto the surface media. A drawback of ink-jet technology is that the delicate ink jets can clog and sometimes vary the quality and tone of the inks. However, manufacturers are working to overcome this problem, and substantial improvements are already in evidence. Ink-jet printers will be strong contenders in the hardcopy market, especially where many colors, good area-fill and fine detail are required. Impact printers are dot-matrix devices commonly used for inexpensive text printing. Although offering low cost and high speed, the marked disadvantage of impact printers is their poor resolution. Color can be attained by inserting colored ribbons. Dot matrix printers are usually used in applications where high volume and low cost are paramount, and image quality is not. Transparent media cannot be used. Cameras are used to copy the CRT in cases where superior image quality and color is needed and cost tends to be a lesser factor. Camera graphics simply involve putting a camera in front of a CRT and snapping the shutter. The result is an image that faithfully reproduces the CRT image. With a camera, 35 mm slides for presentations are easily produced. The cost of camera systems is high, the wait long and the equipment cumbersome. Also, photographic media does not resemble plain paper--it is glossy and hard to write on--and is unpopular as a business document. The use of cameras is limited to applications in which faithful reproduction of a CRT image is a necessity. Finally, thermal technology is employed in some types of plotters and copiers. Thermal technology is similar to electrostatic, except that the ink or media are heat-sensitive, and printing is accomplished with heated print heads. Resolution, speed, device cost and

Selection criteria for graphics hardware cost per copy all can be good for devices using this technology.

Hardcopy selection criteria The determination of the most appropriate hardcopy device for a particular application comes down to five factors: O O O 0 ©

Resolution Speed Color Device cost Cost per copy

Resolution. Vendors usually discuss hardcopy resolution in terms of "dots per inch" or "addressable points per inch." However, differences and subtleties in the way dots overlap often make these criteria meaningless or confusing. A more accurate measure of resolution is "discernible lines per inch." Cameras have a resolution of 200 lines per inch, while dot-matrix printers have a resolution of 100 lines per inch. The unaided eye is the best judge of this factor. Also, the resolution of the copier should match that of the terminal. For example, the resolution of a 200-line-per-inch copier is too high to be used with a 100-line-per-inch CRT. Such a combination would copy the imperfections of the screen onto the hardcopy. Conversely, a copier with resolution much lower than the CRT's would fail to do the screen image justice. Speed. Plotter speed is usually spoken of in terms of"inches per second" to denote pen speed and "Gs" to denote acceleration, although throughput is the most accurate and meaningful measure of plotter speed. For copiers and printers, pages per minute is the key speed factor to look at, since amount of detail doesn't impact print speed. An additional factor to consider on printer plotter speed is the time it takes the host mainframe, or workstation, to "rasterize" the CRT image (if the CRT image is to be copied) to the dot matrix pattern needed for printing. Sometimes this substantially reduces total print speed. For instance, although it may only take 20 sec to print the image, it may take 20 rain to prepare the image for printing. Color. Color is already available in most hardcopy devices, although costs are not yet low enough to make them widely used. Also, most color hardcopy devices (excepting the camera) are as yet unable to exactly reproduce CRT colors. Since hardcopy devices deal with inks and dyes and CRTs with phosphors, it is questionable whether exact matches can be achieved. The need, again, is applicationdetermined. In applications that use color merely for differentiation, exact reproduction is not important; in others, a CRT-hardcopy match could be extremely helpful. Cost. Device cost is usually straightforward but should include all peripheral equipment, such as

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necessary interfaces, standalone rasterizers and software. Cost per copy is arrived at by taking an average of paper, pen, ink, toner and/or film costs. Consider wastage, such as liquid toner that seeps into the paper between copies.

Hardcopy futures Pen plotter popularity will increase, especially in the MIS world, with increased speeds, better human factors design and dramatic price cuts. Applications requiring high resolution and speed will be dominated by ink-jetand electrostatictechnologies.If cost per copy can be lowered for photographic devices, color copies in thismedium willbe more widely used. There will be not only increased competition but collaboration between existing technologies. A possible innovation might be a device that combines existing pen plotter and raster technologies to draw fine detail with plotter skill and fill solid areas with matrix printer techniques. Color will certainly become more prevalent, but the challenge will be to keep costs down. As color terminals become less expensive and more prevalent, hardcopy manufacturers will be hard-pressed to follow suit, since most users want as close a reproduction of the screen image as they can get. Further improvements in quality and cost of color hardcopy units is a certainty. INPUT DEVICES

Current technologies Commonly-used graphics input devices are: digitizers (which include graphics tablets) of various sizes, joysticks, lightpen, mouse and keyboard. Digitizers are, as the name implies, devices which convert analog graphic data to digital data for storage in computer memory. A digitizer can save the user hours of laboriously inputting coordinate points. Digitizers usually consist of a small signal-reading puck and an electronics "tablet" which is underlaid with a grid of wires. A graphics image is aff~ed to the tablet and the hand-held puck moved across the image lines. The user pushes a button on the puck whenever he wants a coordinate point read. Some pucks read coordinates automatically at a constant rate. Because of their simplicity of operation, digitizers are well suited for non-technical users. They can result in extremely accurate images although they are generally more expensive than other input devices. Digitizers have a wider functionality than other devices, as they can be used by a wide range of users for many applications. Joysticks and joydisks. A joystick is a small thin handle which protrudes from the terminal console and is used for moving the cursor around the screen. A joydisk is a small plate which performs the same function. Both are used for on-screen design. Most models, though, are not highly accurate, but they are low in cost. The joystick and joydisk take up little room on the console.

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Thumbwheels. Some terminals have two small wheels, called thumbwheels, that control a fine crosshair cursor horizontally and vertically. The crosshair cursor has access to the full viewable resolution of the display. Lightpens are wands which contain phototransistors in the tip and are used to draw directly on the terminal screen. The constantly moving raster beam in the CRT pulses the phototransistor in the pen and illuminates the points selected. Lightpens are not very fast or accurate and are tedious to use. They are, however, low-cost. Applications for lightpens are limited due to their inaccuracy and relative difficulty to work with. They are usually used for menu selection rather than drawing. Keyboards. Graphic input can be accomplished in its most basic form by simply inputting image coordinate information via the terminal keyboard. Directional arrow keys (left, right, up, down) and "home base" keys make it easy to rapidly move the cursor around the screen. Due to the tedium involved in moving the cursor about with repeating keys, the keyboard is not an efficient input device for involved graphics work.

digitizers will move into the business market and be used for text reading. Becoming increasingly popular in MIS applications is the "mouse", a hand-held digitizer that has no cord or tablet connection. The mouse uses various technologies, sometimes infrared beam, to move the screen cursor relative to the user's hand movements. The mouse represents a highly portable, convenient means of inputting graphic data. Lightpens and joysticks are also becoming increasingly accurate and lower in cost. On-screen design will become more widespread in the future, so lightpen and joystick-type devices will only become more popular. MASS STORAGE

Available technology Mass storage is an increasingly vital element in constructing a graphics workstation. In addition to planning the general storage requirements for operating systems, utilities and programs, users need to understand that graphic images tend to require a great deal more memory than alphanumeric files. Whether data is stored on the host computer or at a local workstation, the primary storage media are:

Input device selection criteria Selection criteria for graphics input devices thus includes: 0 0 0 0

Accuracy Speed Size Cost

Accuracy. The more image coordinates that can be read or input, the clearer the image. Of course, the more coordinates, the greater the memory requirements (and the more expensive). Not all applications need highly resolved input images. Speed refers to the time it takes the user to input data using the device. Size. The size of the device should be in keeping with the layout of an office setting, whether it is to be used by an enginer or a secretary. A digitizer tablet takes up extra room at a workstation, whereas the keyboard, lightpen and joystick are part of the terminal. Cost. As in all graphics hardware, cost impacts the use of different input devices. On a relative scale, digitizers and tablets are the most expensive input media, followed by lightpens, and finally joysticks. Of course, there are low-cost digitizers and expensive lightpens and joysticks. Input device futures Input device futures are aimed at improved accuracy and speed and lower costs. The autodigitizer is a new development that allows faster, more accurate input of image coordinates than manual digitizers. Autodigitization is still confined to scientific applications until manufacturers are able to endow the mechanism with pattern recognition. At that point, auto-

O Tape O Hard disks O Floppy disks

Tape. Traditional tape drives, usually connected to the host computer, provide higher capacities and access to shared data, but communications from the host to the workstation can be very expensive and result in poor response times. Most graphics applications rely on host storage to some degree and will for some time to come. However, the emphasis is shifting to local storage as the cost per byte of mass storage continues to decline. In larger systems, tape is useful for backup. Harddisks. Local workstation storage is usually in the form of hard disks and is the optimum arrangement for graphics applications. The key reason is greater user interactivity: the user can download pertinent data from the host to his workstation and perform all graphics processing locally. He need only depend on the host when new source data is required or when complex mathematical processing is demanded. Local storage tends to improve response times, as well. Floppy disks. Floppy disks are used primarily for I/O transportability functions and short-term graphics routines. Due to their volatility and capacity restrictions, floppies are not the optimum choice for primary storage or backup. Storage device selection criteria Selection criteria for storage devices include: O Capacity O Interactivity O Transportability

Selection criteria for graphics hardware

Capacity is simply how much the device will hold. Floppy disks hold the least amount of data, tape drives the most; they are priced accordingly. lnteractivity. Interactivity is the measure of how easy and fast it is to communicate with the host computer and is determined by file management capabilities and access times. Graphics work can require a great deal of interaction with the CPU. If the user is one of a large network of terminals talking to the same CPU, response time can be long and frustrating. Local storage, usually as part of an intelligent terminal, gives the user independence from the host computer for most of his transactions and results in greatly improved response times. (For more information on the interactive advantages of local storage, refer to the "Intelligence" section under "Additional terminal considerations" in this paper.) Transportability. Transportability indicates the ability to remove and use media for backup and data sharing. Floppy disks are by design easily transportable but have limited storage capacity. Hard disks may not be removable but have significantly greater storage capacity. Tape media are transportable and have storage capacity but very limited interactivity. Selection of appropriate storage media depends upon application requirements. Future storage technologies Winchester disks are emerging as the primary storage medium for graphics applications due to their high capacity, small size and low cost. Local area networks will feature file servers for multiple workstations, wherein large amounts of data stored on hard disk can be efficiently and cost-effectiveiy shared by many users. Tapes will be used primarily for backup and floppies for short-term operations. APPLICATION REQUIREMEN'IS---THE B o T r o M LINE IN SELECTION CRITERIA

The graphics hardware marketplace today can be confusing. The buyer must know his present and near-future application needs and remember that every feature has its cost. He should also keep in mind that speed, high resolution and color are unimportant in many applications. Even within an MIS environment, the requirements for graphics terminals are diverse. Bar charts and simple line graphics requiring many colors, areafill and only moderate resolution are excellent raster

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candidates. Detailed business analyses may not need color but may demand sharp resolution--perhaps best served by a vector refresh display. Complex graphics requirements calling for high interactivity, high resolution and dense images may require the strengths of the sophisticated raster and vector displays commonly used in CAD~CAM applications. Many vendors offer firmware (plug-in boards or modules) capable of giving non-graphics hardware graphics capabilities. For instance, some manufacturers can convert their standard text-printing alphanumeric terminals into graphics terminals. Room lighting, frequency of use, the technical proficiency of the user, number of users, and the presence or absence of distributed data processing will impact other terminal-related decisions: the physical packaging, intelligence level, data communications capabilities, and availability of softkeys. In the hardcopy arena, pen plotters are well-suited for high resolution, color, line-graphics images that do not require dense area-fill or speed. Copiers are best for rapidly produced, low-cost, high-resolution copies used for presentation or archival, and printer plotters produce high-resolution line-graphics, although at a higher cost than pen plotters and copiers. Impact printers are excellent means for rapidly producing hardcopy at low cost where resolution is unimportant. Camera systems offer the best resolution and color and are useful for producing 35 mm slides, but the cost is highest of all hardcopy devices and the wait long. Digitizers are often the best choice for MIS graphics work due to their ease of use, their accuracy and their flexibility. Joysticks and lightpens are exact for complex work but can be fatiguing to work with for long periods. Keyboards do not offer the human factors engineering that the other devices do, but they can be used for inputting simple graphics images. Portable Winchester disks will be the primary storage medium for graphics workstations in the near future, with tape being used for backup and floppies for short-term storage. Shared data stored in central repositories will become more common as data communications networks become more widespread. The future holds a tremendous variety of graphics applications and users. Hardware selections should be carefully matched to both, since manufacturers are producing ever more sophisticated products, and it is easy to over-buy for your needs.