this merely by pointing the light pen at the element and pressing an 'accept' button. The light pen photomultiplier produces a pulse at the instant the selected element is painted, which signals the computer. Since the address of the element being painted is known by the computer, its identification can be used as directed by the program. For example, the element may be erased, moved, duplicated, or rotated. By proper programming, symbols or labels on the screen can be made lightpen sensitive and can be selected by pick function. This operation may be used to select a single option from a list or 'menu' of alternatives presented on the display." (Prince, 1966, p. 1699).

"After investigating several possibilities, we concentrated on the use of intensification for highlighting parts of a display. For example, the four boundary lines of a surface may be brightened while the interior lines are dimmed. This technique of varying intensification has proven to be an important piece of feedback to the console user. We call the preceding example 'static' intensification because an item remains intensified throughout the current display. Static intensification can be used meaningfully in other ways, besides highlighting. For example, user attention can be focused on suggested choices of control words by brightening them, while dimming the rest of the display. Shading to give a three-dimensional effect is also useful in optimizing the user's understanding of a display. This technique, however, requires enough intensity levels so that the transition between them is continuous and imperceptible . . .

"This 'selective disabling' aids the operator in recognizing his displays as a composition of various sets of items. In addition, he will be less confused when trying to make a selection. Only a small subset of items can be selected, even though other information is still displayed. Thus, the selectable items are kept in context with the rest of the display. The combination of selective disabling and dynamic intensification provides the means of conveying the syntax of a graphical language to the console user. (Joyce and Cianciolo, 1967, p. 715).

4.18 "Overlays can be quickly accomplished on standard maps by reading the maps with the computer-controlled CRT reader and combining them in memory with elements to be displayed. The results can be put out on film." (Fulton, 1963, p. 40).

4.19 Motivational factors obviously include the assurance (or lack of assurance) to the client that he is in fact effectively online to the processing system; that he has, in effect, direct access to his own prior program and data stores and to such other programs or data as can be shared; and that his own data banks and programs are adequately protected against unauthorized access, piracy, or inadvertent destruction.

"Evaluating the 'cost effectiveness' of graphical I/O of various types is a particularly difficult task. The literature is noticeably lacking in any reference to the subject. Given a particular function to im

plement, such as to reduce a graph to hard copy, to monitor a given equipment or program parameter, or any other straightforward operation, a cost/performance comparison of alternative implementations can be made. However, to assign a widely agreed upon numerical scale of values to human productivity or 'intellectual enhancement' is difficult, if not impossible." (Wigington, 1966, p. 88).

"The art of designing man-machine systems is still in its infancy. List selection terminals, by placing the output burden on the data system, are able to increase the input rate that an untrained user can achieve. By so doing, terminal operation is made feasible for a much broader class of users. So far this approach has proved useful in applications in which the vocabulary is limited to several hundred words. We are just beginning to develop the automatic formatting procedures that will expedite the design of the next generation of matrices. The potentials of information systems that adapt to the user's response patterns are yet to be realized. To the retriever, this approach offers the ability to control the quality of the data at the time that they are entered without, we hope, placing an undue burden on the enterers Although we have been heartened by our limited successes in facilitating man-machine communication, we have at the same time been humbled and challenged by our ignorance of how a dialogue should be structured, how we should mold the machine to fit the man. It is perhaps in this area that the next advances will be made.' (Uber et al., 1968, p. 225).

design

4.20 "In order for computer-aided to achieve its full potential in the coming years, significant hardware advances are called for in several areas. More natural means for communicating with the computer are desirable. Although many clever techniques have been developed for using the light pen, it is still not completely satisfactory. Also, the need is sometimes expressed for large, high-resolution 'drawing board' displays." (Prince, 1966, p. 1706).

"A variety of light pen configurations are available ranging from a simple penholder type to a gun type. Some pens are relatively heavy while others are lightweight. Some use a very flexible cable and others use a rather stiff cable or coil cord. Aiming circles are provided with some light pens so that the operator knows where the sensitive area of the light pen is pointed. Activating switches for the light pen include mechanical shutters on the pen, electrical switches on the pen, knee switches and foot pedal switches." (Machover, 1967, p. 158).

4.21 "Another difficulty of the lite pen is that its broad end which contacts the scope face obliterates that portion of the screen where the lite pen is acting. One means of overcoming this difficulty might be to display the points drawn by the pen to one side of the area actually sensed." (Loomis, 1960, p. 9).

4.22 "Display maintenance has been provided by the large computer or by a data channel off the large computer. The high transfer rates needed for such an organization have dictated that the consoles be very close, if not physically adjacent, to the supporting computer or channel." (Ninke, 1965, p. 839).

. . . Display maintenance is independent of control computer intervention. Thus, once started by the control computer, the display continuously refreshes itself with a direct jump word at the end of the display picture providing the link back to the start." (Ninke, 1965, p. 842).

"To avoid flicker and to update picture information, each point of the display must be repeated at least every 1/50 second. Although high-speed repetition is within the capability of light-deflection methods, rapid repetitive presentation is unnecessary if the display screen has good persistence." (Soref and McMahon, 1965, p. 60).

"Memory for a vector display file requires about 4K words of storage per user." (Roberts, 1965, p. 217).

4.23 "Operable flat oscilloscopes have been constructed and have proved to afford excellent resolution." (Licklider, 1965, p. 96).

4.24 For example, "the most difficult aspects of the keyboard to experiment with are the key pressure required and the reaction and travel of the keys at the moment the signal is transmitted.” (Boyd, 1965, p. 157).

"The keyboard design would be based on principles of motion study. Each key would be shaped and positioned for maximum accessibility by the shortest route, with compensations made for distances traveled, varying strength in different fingers, and other factors." ("The (R)evolution in Book Composition . . . IV", 1964, p. 69).

"The keyboard must be kept fairly small, at least within the span of an operator's hands. In effect, this does mean a single alphabet keyboard whose condition is controlled by function buttons." (Boyd, 1965, p. 157).

. . . Various criteria such as weight of key depression, key travel, key spacing, layout, and whether or not you want hard copy." (Boyd, 1965, p. 153).

"One possible result of this type of analysis could be a bowl-shaped keyboard, with keys on the sides and rear banked up from the horizontal . . . This would enable the fingers to reach outlying keys by moving in a straight line, rather than in an arc or in two moves, over and down. Another feature would be larger keys on the outskirts, to reduce the need for accuracy in moving fingers long distance." ("The (R)evolution in Book Composition . . . IV”, 1964, p. 69.)

"Kroemer (1965) . . . arranged the keys in two separate but symmetrical groups, one for each hand. Each group consists of three curved rows of five keys. The form of the curve corresponds to that of the fingers and the possible movements of the individual fingers. The two space bars for the

thumbs are curved as well, which enables the thumbs to strike them from any hand position. The keyboard position is no longer horizontal since tests disclosed that an angle of 30°-45′ to the horizontal gives the most comfortable position to the hands and arms." (Van Geffen, 1967, p. 6).

Hobbs points out further that "new types of keyboards are being developed that do not involve mechanically moving parts and that may permit more design freedom from the human factors standpoint. These include pneumatic, optic, and piezoelectric techniques." (Hobbs, 1966, p. 38).

4.25 Mills, in a review of 1966 developments, concludes that "work directed toward solving this interface problem has appeared to be poorly focused. Only a few attempts to specify an improved general-purpose terminal were reported, and even fewer reports of actual hardware development and prototype testing were discovered." (Mills, 1967, p. 245).

Further, "it will require major research and engineering efforts to implement the several functions with the required degrees of convenience, legibility, reliability, and economy. Industry has not devoted as much effort to development of devices and techniques for on-line man-computer interaction as it has to development of other classes of computer hardware and software." (Licklider, 1965, p. 66).

4.26 "Specific to the time-sharing field there is a need for the development of adequate consoles, especially graphical input-output consoles. There are conflicting requirements for low cost and for many built-in features that minimize the load on the central computer. An adequate graphical console may require built-in hardware equivalent to that required in a fairly sophisticated computer. This is an area in which analogue as well as digital techniques may be important. It is an area in which the new component technologies may make significant contributions." (Rosen, 1968, p. 1447).

"Design efforts are directed towards realizing a console that uses a cathode-ray tube (CRT) display with approximately 1,800 alphanumeric-character capacity. The data-communication between central computer and console will initially be 200 characters per second with provisions for higher data rates. Several character sets should be possible in addition to the English alphabet. User communications are entered by means of a typewriter keyboard, and special function buttons which designate frequently encountered commands. The user's message is displayed on the CRT prior to the transmission to the time-shared computer, and editing of displayed commands is possible. As the user's conversation with the catalog system progresses, certain data supplied by the computer may be stored locally for future reference, edited as required, and eventually printed in hard-copy form." (Haring, 1968, p. 37).

4.27 "On the hardware side the picture seems to be much brighter, at least in terms of providing

color-display systems of greater color fidelity and reliability." (Rosa, 1965, p. 413).

4.28 "Color is deemed a necessary feature because it can reduce errors and increase the assimilation of displayed information." (Mahan, 1968, p. 34). 4.29 "To produce a stereographic display the computer calculates the projected video images of an object, viewed from two separate points. The resulting video maps are stored on separate refresh bands of the rotating memory. The two output signals are connected to separate color guns of a color television monitor, thus creating a superimposed image on the screen. Optical separation is achieved by viewing the image through color filters.

"The display is interactive and can be viewed by a large group of people at the same time." (Ophir et al., 1969, abstract, p. 309).

4.30 "Unsolved problems. . . that derive from the graphic themselves include flicker, ease of use, coupling of programs to do substantive computations, the language of discourse, and the desirability of halftone capability." (Swanson, 1967, pp. 38-39).

"Although the display field has progressed rapidly during the past five years, significant future progress is still required to provide the types of displays necessary to achieve the essential close man-machine interaction at a price that will permit their widespread use. Several major needs and problems facing the display field have been discussed here, including the need for:

(1) better methods of implementing large-screen displays which can provide dynamic realtime operation with both alphanumeric and graphical data

(2) flat panel visual transducers for both largescreen and console displays that:

(a) can be addressed digitally

(b) provide storage inherent to the display panel

(c) are compatible with batch-fabricated electronics and magnetics

(3) better determination of the proper functions to mechanize in the display to facilitate the human interface, including the appropriate human factors determination of the appropriate trade-offs between manual and automatic functions

(4) more effective software both to facilitate the programming of display functions and to provide for the efficient computer generation and control of operations such as the rotation and translation of drawings and the interrogation of large data bases

(5) lower cost for all categories of displays, but particularly for low performance remote display consoles.

Developments or improvements needed in specific display technologies (e.g., the need for higher

power or ultra-violet lasers) have also been cited.” (Hobbs, 1966, p. 1882).

4.31 "There are

areas which I believe deserve priority attention. The first is the development of a small, cheap, convenient desk-top terminal set such as the duffer unit.” (Mooers, 1959, p. 38).

"Whereas fast time sharing divides the cost of the computer itself among many users, there is no comparable way to distribute the cost of users' input and output equipment. Therefore the problems of console design and development are critical. Teletype equipment is inexpensive and reliable, but the character ensemble is small, and this seems likely to limit the applicability of teletype seriously. Electric typewriters are more expensive and less reliable, but they provide a reasonably large set of characters (enough, for example, to handle ALGOL with only a few two-stroke characters), and they may be adequate for the input and output requirements of the majority of users. If they are not, then almost surely the next requirement is a drawing board or 'doodle pad' onto which both the operator and the computer can write and make graphs and diagrams. These functions are now instrumented with oscilloscopes; what is needed is a less expensive means. (Licklider, 1964, pp. 124-125).

"Displays are good, but, in the generalized form needed, they tend to be expensive. This means a reduction in physical accessibility, since one does not put a $50,000 or $100,000 box in every office. Displays which are both low-cost and adequate do not exist." (Mills, 1966, p. 197).

4.32 "William N. Locke (MIT) reported briefly on INTREX . . . an MIT Lab is trying to develop a better console because the small consoles are not now very satisfactory." (LC Info. Bull. 25, 90 (2/10/66).)

"Effective testing of user interaction with the augmented catalog requires a remote computer console optimally suited to the task. Currently available consoles, serious consoles, however, exhibit shortcomings as regards catalog experimentation. Impact-printing teletypewriters operating at ten to fifteen characters per second, for example, are clearly too slow for rapid scanning of large quantities of bibliographic data. The cathode-ray-tube (CRT) alphanumeric display terminals now offered by several manufacturers do allow for more rapid, quiet display of computer-stored data. However, they, too, lack features essential to effective user interaction with the augmented catalog. For instance, there is generally a lack of flexibility in operating modes, in formats (e.g., no superscripts and subscripts) and a severe limitation on the size of the character set. On the other hand, the CRT graphic display terminals that are currently available can be programmed to circumvent these deficiencies but are very expensive as regards original cost, communications requirements, and utilization of computer time." (Haring, 1968, pp. 35-36).

4.33 "How much is the end user willing to pay for his terminal? What does he expect for it? What could he do without? The terminal's requirements are obviously going to vary with the application program." (Stotz, 1968, p. 16).

"The need for graphical displays at a large number of terminals remote to the utility places a severe constraint on the allowable cost per display unit." (Dertouzos, 1967, p. 203).

66

Typically, the R & D requirement is noted for ... lower cost for all categories of displays, but particularly for low performance remote display consoles." (Hobbs, 1966, p. 1882).

4.34 "In the multiple-access system environment, point-by-point generation of the display by the main computer results in the imposition of intolerable loads on the processor. The task of simply regenerating a fixed picture, involving no new information, can occupy a major part of processor capacity." (Mills, 1965, p. 239).

"Also, if such high speed consoles are to be used remotely, local display maintenance is essential. Thus, a picture need be transmitted only once, maybe over low-cost low-speed lines." (Ninke, 1965, p. 840).

"There is an increasing trend toward using small satellite computers for local servicing of the immediate demands of the display and the human operators while communicating with a large timeshared computer for complex computations." (Wigington, 1966, p. 88).

"Many modern computers have a memory configuration which can be used to refresh the display without interrupting other computations. Where this is not possible, a buffer memory is available within a display. Commercial terminals use core memories, delay lines, and drums. With the availability of low cost, high-speed, general purpose, digital computers, it becomes feasible to consider including a digital computer in the CRT graphic terminal. BR, DEC, and IDI offer terminals in which the digital computer is an integral part of the display and provides functions of storage, plus some of the hardware mode control features.' (Machover, 1967, p. 153).

"There is growing awareness that display buffers should, in fact, be small general purpose computers, which opens up a whole new spectrum of possibilities in properly assigning tasks within the overall system." (Ward, 1967, p. 49).

"The concepts of list processing have proven to be desirable in the manipulation of display data. Second, the hardware and software design of MAGIC . . . provides sufficient local processing abilities to significantly remove the burden of display data processing from the C.P.U. to which it is to be interfaced." (Rippy et al., 1965, p. 829).

...

"The display material memory is an Ampex RVQ core unit with 4096 36-bit words and a 5 microsecond cycle time. This storage capacity represents about eight large pictures, i.e., those which take

about 1/30-th of a second to display." (Ninke, 1965, p. 841).

"The remote operation of displays is facilitated if local storage is provided at the display for refreshing the picture. Thus only changes need be transmitted from the central computer, and the data transmission requirements are greatly reduced. Also, some computing capability can be placed at the display so that change of scale, translation, rotation, and other modest computations can be done locally. In this regard, M.I.T. and others are experimenting with satellite computers which can continuously refresh several displays and perform simple calculations for them, but which call upon a larger computer for extended computation." (Prince, 1966, p. 1706).

4.35 "The Control Edit Console consists of two dark trace storage tubes and associated equipment for control and operation. The dark trace storage tube, and its associated equipment, is a device which will store and display a single frame of video scan for a relatively long period of time (up to several days). It has excellent resolution of up to 500 or more line pairs per inch . . . Through manual control it is possible to erase and edit portions of the display. By using two DTS tubes, it will be possible to duplicate the graphic portions of the original document on the second tube. The display on the first tube will, of course, retain the original document for reference purposes. The selective transfer is accomplished by XY coordinate sliding markers, or by tracing area boundaries with electrostatic or infrared pencil directly on the screen . . ." (Buck et al., 1961, p. VI-21).

4.36 "Bunker-Ramo communications devices lend themselves particularly well to engineering applications. The results of the computations requested by the engineer may be displayed in a meaningful format he is accustomed to seeingsuch as a Nyquist plot, or families of plots, for any number of variables." (Dig. Comp. Newsletter 16, No. 4, 37 (1964).)

4.37 "No matter what logic is applied to the management of the data base inside the machine, the surface appearance of the data base must be under the user's on-line control. He should be able to set up the file display, the object and property names, the formats of these files, including sequence and arrangement of data as he desires. He should be able to generate, store and revise the structure of his displays, on-line . . ." (Bennett et al., 1965, p. 436).

For these reasons, it is suggested that "display equipment manufacturers [should] improve and provide software packages that allow:

a. One, two, or three variable-width column page formats with justification routines and masking provisions for inserting graphics.

b. Variable character spacing to improve text density,

c. Variable line spacing to allow text with or without superscripting and subscripting, and d. Utilization of the software packages on additional general purpose digital computer systems." (Burger, 1964, p. 12).

4.38 For example: "To qualify as standard, a terminal device must operate on-line, use a voice grade channel, provide a visual display, at a rate taxing the reading and scanning speed of the proficient user." (DeParis, 1965, p. 49).

"A reasonable goal is that the console should sell for under $15,000, that it should have a cathode ray tube or something equivalent, that it should allow for some buffering of information, and that it should have a flexible and adaptable keyboard structure and status information display." (Bauer, 1965, p. 23).

"Certainly the design of the user's terminal is important; but far too much emphasis seems to have been placed on high style and novelties to the detriment of dependability and economy." (Adams, 1965, p. 486).

"This terminal equipment should be small. It should be easy to use, since this is to be the main channel of intercommunication between the human worker and the machine system. .

"The terminal equipment should provide a typewriter-style keyboard for input, and it should have an alpha-numeric printing device for printing its output. Its output should be printed on paper, either on a paper sheet or on a paper 'ticker tape' with a gummed back. Thus the output can be assembled and edited by scissors and pasting." (Mooers, 1959, p. 10).

"If any of these qualities [good resolution, no flicker, upper and lower case] are badly deficient, the reading becomes so difficult that the type of person required to understand and edit complex information will refuse to use the display." (Buckland, 1963, p. 179).

"To allow a user, however, to do real-time composing, editing, or other manipulation of graphical information with a light pen or other graphical device, the sum of access time and transmission delay must be only a few milliseconds." (Ninke, 1965, p. 840).

"It would seem that an automated system, to be completely satisfactory, has to respond within. a few seconds and should present output results at roughly a normal reading rate." (Drew et al., 1966, p. 6).

"The display should have controllable persistence. and should be free of flicker." (Licklider, 1965, p. 94).

"Upper and lower case alphabetics should be provided; two symbols should be able to be plotted at the same position on the screen (for underline, circumflex, etc.); and superscripts and subscripts should be possible. Both the computer and the user should be able to set Tabs and their settings should show at a glance." (Stotz, 1968, p. 17).

4.39 "We should like to have: a color display... if possible, or, if not, a black-on-white display. . . with at least eight gradations of brightness . . . and a resolution exceeding 400. . . or 200 . . . or, at any rate, 100 ... lines per inch." (Licklider, 1965, p. 94).

While eight levels of gray scale may be adequate for many user-oriented remote terminal inputoutput units (and more is sometimes available), far more is required for sophisticated pictorial data processing.

Ledley's FIDAC (Film Input to Digital Automatic Computer) currently provides only eight gray levels for a 700×500 input spot raster. (Ledley et al., 1966, p. 79).

"Digital Electronics Inc. L-SCAN rapidly converts visual data, such as drawings and objects, into digital format for computer analysis and record storage. It uses a vidicon tube pick-up and records on IBM compatible magnetic tape. The unit can discriminate 64 shades of gray and has a field of view divided into 40,000 segments." (Data Proc. Mag. 7, 50 (Feb. 1965).)

"Interest is developing in extensions of the display technique to include color and grey scale. It seemed likely from the earliest experiments that the use of phosphors inside the cells could be used in multi-color displays. The later observation of ultra-violet radiation in the cells led to the idea that this radiation could excite phosphors deposited on the outside of the outer glass panels, and that the effect should be enhanced if the panels were made of quartz or some other material with good U V transmission characteristics." (Arora et al., 1967, p. 11).

"The practical application of such displays as chromatron photochromic dyes, coupled with such reproduction means as thermoplastic recording or smoke printing will usher in an era of true electronic printing in all the flexibility we have come to expect in printed communication." (Herbert Ohlman, panel discussion of Markus, 1962, p. 25).

Further, "the National Aeronautics and Space Administration has awarded the Philco Corp., two contracts to develop an experimental color television display system for possible use in the mission control center of the Manned Spacecraft Center in Houston." (Electronics 38, No. 18, 40 (1965).)

4.40 "Most experienced users want 'terse' modes of expression to the computer and full, unabbreviated (and fast) responses from the computer." (Licklider, 1965, p. 182).

"It should be possible, in a ‘debreviation' mode, to type 'clr' on the keyboard and have "The Council on Library Resources, Inc.' appear on the display." (Licklider, 1965, p. 100).

"Several types of keyboarding shortcuts have been developed; for example, computer programs automatically provide italicized and capitalized characters in chemical names, and the computer