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permits the generation and manipulation of the graphical data structure, and provides statements for controlling real-time man-machine interaction. The interaction portion of the language is used with the GRAPHIC-2 graphical terminal. The rest of the language pertains to the common data structure used by all graphical devices and terminals.” (Christenson and Pinson, 1967, p. 705).

“The PLOT operator is used to create a picture on the oscilloscope corresponding to the graphical language statements . . . It builds a list of .console commands' (plot a point, or a line, reposition the beam etc.) known as the display file, which are interpreted by the display console hardware so producing the desired picture.” (Lang et al., 1965,

programmer. As an example of a high-level system, we can mention the formal language LEAP, in which the programmer can easily manipulate the logical elements of his model, and the structuring of the information in the form of hash-coded tables) is performed automatically by the language system. At the other extreme we have a language like L6 which is a macro language useful in creating arbitrary list structures. The difference between these two ‘graphical languages' is so great that one could easily conceive of implementing the LEAP language using the L6 language. An excellent review of this subject is given by Gray." (Laurance, 1968, p. 387).

"Only two other compiler-compiler systems which cater for graphics, with Computer Aided Design in mind are known to the author. The first of these, AED, due to Douglas T. Ross is a very long-standing and general systen of great interest. GULP only attempts a small part of this generality; as AED has been justly called “a system of systems for building systems'. AED processes graphic language using a macro-processor in a different way from the character definition of GULP. AED is also able to deal with contextdependent languages, and with more general types of precedence besides including an ALGOLlike compiler and many special-purpose packages for design; e.g., POLYFACE.” (Pankhurst, 1968,

p. 39).

p. 416).

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“VITAL (Variably Initialized Translator for Algorithmic Langauges), a general purpose translator for the Lincoln Laboratory TX-2 computer, is currently being adapted for use as a graphical control language translator.” (Roberts, 1966, p. 173).

“The MAD language offers a powerful facility to programmers to tailor their compiler to fit their application, viz., the MAD operator-definition facility. Using this part of the MAD compiler, the programmer (or programming staff) can extend the compiler by introducing new operators and new operand mode definitions into the language. In the formulation of any graphical language, the MAD operator-definition facility should play a large role. The syntax extensions we are describing in this paper are those which cannot be encompassed within the operator-definition facility. The listprocessing facilities described in the last section resulted from the examination of the L6 syntax, and the identification of these elements which were beyond the scope of the operator-definition ability. The rest we leave for development at the MAD programming level.

“In a similar fashion, we have tried to identify those elements of graphical language which were beyond the scope of the MAD syntax for their possible incorporation into the compiler. The one example of a graphic language which encompasses most of the desirable elements is the LEAP language of Feldman and Rovner. This language is an ALGOLtype language which includes elements of set operations as well as Feldman's own method of representing graphical relations. LEAP is predicated on a highly elaborate but efficient method of data storage involving hash coding, but the details of the implementation do not concern us here. What does concern us, however, is the language syntax, insofar as it is incompatible with a MAD representation.' (Laurance, 1968, p. 392).

“The subject of data structures has received a great deal of attention in the past few years, especially in relation to computer-aided design. Programming systems used for creating data structures (sometimes dignified by the name “graphical languages') vary greatly in the rigidity of their representation and the types of facilities offered to the

"It is of vital importance that the language facility for the Computer-Aided Design System include not only flexible descriptive and programming languages in word form, but a generalized capability for graphical communication as well. There are many aspects of design in almost any field, for which the natural means of expression is in terms of pictures or diagrams, and any attempt to convey equivalent information in verbal form would be extremely unnatural and awkward, and would defeat the basic principle that the designer-user be able to operate in a manner which is natural to him.” (Ross and Feldman, 1964, p. 15).

4.14 "Even within equipment classes there is a wide variation in keyboard arrangements. Though the alphanumerics generally correspond, the availability and location of special characters is by no means standard. Functional controls are even more varied, and in the case of devices using complex editing features (the alphanumeric display device) the number, type, function, and placement of functional controls is completely dissimilar between manufacturers. (Auerbach Corp., SDA, 1967, p. 2–10).

“For the inquiry/display console, the major problem is that of determining the proper functions to implement for the user.” (Hobbs, 1966, p. 44). “Other operator input devices are available

various consoles. Alphanumeric keyboards and function keys are used. Some function keys use plastic overlays for additional coding. Track

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balls and joy sticks are preferred by some users. available programming languages.' (Newman, The Rand Tablet, which provides an easy method 1968, p. 47). for graphic input, is available as an accessory "The major problem is the development of in several systems." (Machover, 1967, p. 158). sufficiently versatile programming languages di

"About a half of the available buttons are left rected at graphic, interactive devices.” (Flynn, unprogrammed, so that every user

can tailor

1966, p. 99). the system to his own particular needs by con- "Unlike conventional

computer languages, structing just those operators which are useful graphical languages have received little study, and to him at a given moment. A paper overlay is used their formal properties have not been examined in to mark the labels under the buttons ... The depth. The lack of precise ways to formulate and system provides operators

operators which

which allow each represent graphical language fundamentals impedes user to keep his own private programmed push- the use of graphical techniques in many problem buttons and functions in a deck of cards. The areas.” (Sutherland, 1967, p. 29). same programmable buttons may then be utilized 4.16 “The types of phosphors used in current by different users for completely different purposes alphanumeric display terminals are of relatively low simply by reading in a small deck of cards at the persistence. To present a display that is suitable start and punching out a new deck when someone for viewing and free from annoying flickering, the else wants to use the system.” (Clem, 1966, p. 136). display must be continually regenerated. Buffer

“Registration is important in systems using storage is provided within the central controller or multiple display projectors or sources. Display within each display unit to store data entered locally overlays are a prime example where static informa

or received from the remote computer. Logic tion is projected over the dynamic display. It is circuitry within the controller or display unit utilizes very important that the images are properly regis- the buffer storage to regenerate the display, usually tered with respect to each other. In general, 30 to 40 times per second." (Reagan, 1967, p. 33). registration accuracy should meet or exceed the “Continual regeneration of a short persistence resolution of the display in order that misregistration CRT for flicker-free viewing demands high data not be detected." (Mahan, 1968, p. 5).

transfer rates, or considerable buffer storage; but in “... Better determination of the proper func- return for this outlay comes ready communication tions to mechanize in the display to facilitate the by single photosensor pens and a medium for highly human interface, including the appropriate human dynamic displays. However, the attendant costs are factors determination of the appropriate trade-offs related to regeneration rates established by persistbetween manual and automatic functions." (Hobbs, ence of vision criteria and are disproportionate to 1966, p. 1882).

the dynamic content of the majority of displays “In addition to the standard typewriter keyboard,

where static text and diagrams prevail for seconds." the CRT set will contain 40 special function keys as

(Rose, 1965, p. 637). well as several cursor control keys. Through the use

"While the maximum required number of flickerof plastic overlays, the meaning and purpose of the

free lines varies greatly among applications, a special function keys can be changed when the

vector construction rate of 10 microseconds per

inch for the larger component, plus a memory sets are used for different application modes." (Porter and Johnson, 1966, p. 81).

access and decode time of not more than three

microseconds per vector, should satisfy the require“Manual input to the (IBM 2250] display unit is

ments for most applications. A refresh rate of 30 effected by one of three devices – an alphanumeric

frames per second would display about 2,600 conkeyboard, a program function keyboard and a light

nected one-inch lines." (Chase, 1968, p. 26). pen ... The program function keyboard contains

4.17 “By modulating the electron beam with 32 keys designed to allow the operator to indicate

several differential selectable frequencies, one could program interpretative functions to the computer

'color' or 'classify' various displayed points on the by means of a single key depression . . . Any

CRT screen." (Haring, 1965, p. 854). significance can be ascribed to ... [the keys]

“The light pen allows good feedback in pointing depending upon the requirements of the operator

since programming can brighten what unit is being and the program.” (“IBM System/360”, 1965, pp.

seen, or display only the total unit being seen. The 298–299).

importance of such feedback cannot be appreciated 4.15 “A system is described in this paper for until one works with a graphical system.” (Ninke, developing graphical problem-oriented languages. 1965, p. 844). This topic is of great importance in computer-aided "In addition to selecting point locations by means design, but has hitherto received only sketchy of the tracking cross, the light pen can be used in documentation, with few attempts at a comparative another interesting mode of operation known as the study. Meanwhile displays are beginning to be used pick function. After a figure has been drawn by the for design, and the results of such a study are operator, or is generated on the basis of computed badly needed. What has held back experimentation data, the operator may desire to select a particular with computer graphics has been the difficulty of

curve, component, line of text, or other distinct specifying new graphic techniques using the element which is a part of the picture. He may do

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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 meaning. fully 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 1/0 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 enter

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).

, 4.20 "In order for computer-aided design 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 avail. able ranging from a simple penholder type to a gun type. Some pens are relatively heavy while others are light weight. 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).

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p. 217).

4.22 “Display maintenance has been provided thumbs are curved as well, which enables the by the large computer or by a data channel off the thumbs to strike them from any hand position. The large computer. The high transfer rates needed for keyboard position is no longer horizontal since tests such an organization have dictated that the consoles disclosed that an angle of 30°-45' to the horizontal be very close, if not physically adjacent, to the

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gives the most comfortable position to the hands and porting computer or channel." (Ninke, 1965, p. 839). arms." (Van Geffen, 1967, p. 6).

... Display maintenance is independent of Hobbs points out further that “new types of keycontrol computer intervention. Thus, once started boards are being developed that do not involve by the control computer, the display continuously mechanically moving parts and that may permit refreshes itself with a direct jump word at the end more design freedom from the human factors standof the display picture providing the link back to the point. These include pneumatic, optic, and piezostart.” (Ninke, 1965, p. 842).

electric techniques.” (Hobbs, 1966, p. 38). "To avoid flicker and to update picture informa

4.25 Mills, in a review of 1966 developments, tion, each point of the display must be repeated at

concludes that “work directed toward solving this least every 1/50 second. Although high-speed

interface problem has appeared to be poorly repetition is within the capability of light-deflection

focused. Only a few attempts to specify an improved methods, rapid repetitive presentation is unneces

general-purpose terminal were reported, and even sary if the display screen has good persistence.”

fewer

eports of actual hardware development and (Soref and McMahon, 1965, p. 60).

prototype testing were discovered." (Mills, 1967, “Memory for a vector display file requires about

p. 245). 4K words of storage per user." (Roberts, 1965,

Further, “it will require major research and

engineering efforts to implement the several func4.23 “Operable flat oscilloscopes have been

tions with the required degrees of convenience, constructed and have proved to afford excellent

legibility, reliability, and economy. Industry has resolution.” (Licklider, 1965, p. 96).

not devoted as much effort to development of 4.24 For example, "the most difficult aspects of

devices and techniques for on-line man-computer the keyboard to experiment with are the key

interaction as it has to development of other classes pressure required and the reaction and travel of the

of computer hardware and software.” (Licklider, keys at the moment the signal is transmitted."

1965, p. 66). (Boyd, 1965, p. 157).

"The keyboard design would be based on princi- 4.26 “Specific to the time-sharing field there is ples of motion study. Each key would be shaped a need for the development of adequate consoles, and positioned for maximum accessibility by the

especially graphical input-output consoles. There shortest route, with compensations made for dis- are conflicting requirements for low cost and for tances traveled, varying strength in different many built-in features that minimize the load on the fingers, and other factors.” (“The (R)evolution in

central computer. An adequate graphical console Book Composition ... IV”, 1964, p. 69).

may require built-in hardware equivalent to that “The keyboard must be kept fairly small, at

required in a fairly sophisticated computer. This is least within the span of an operator's hands. In

an area in which analogue as well as digital techeffect, this does mean a single alphabet keyboard

niques may be important. It is an area in which the whose condition is controlled by function buttons.”

new component technologies may make significant (Boyd, 1965, p. 157).

contributions.” (Rosen, 1968, p. 1447). ... Various criteria such as weight of key

"Design efforts are directed towards realizing a depression, key travel, key spacing, layout, and

console that uses a cathode-ray tube (CRT) display whether or not you want hard copy.” (Boyd, 1965,

with approximately 1,800 alphanumeric-character p. 153).

capacity. The data-communication between central “One possible result of this type of analysis could

computer and console will initially be 200 characters be a bowl-shaped keyboard, with keys on the sides

per second with provisions for higher data rates. and rear banked up from the horizontal . . . This

Several character sets should be possible in addition would enable the fingers to reach outlying keys by

to the English alphabet. User communications are moving in a straight line, rather than in an arc or in

entered by means of a typewriter keyboard, and

special function buttons which designate frequently two moves, over and down. Another feature would be larger keys on the outskirts, to reduce the need encountered commands. The user's message is for accuracy in moving fingers long distance." displayed on the CRT prior to the transmission to (“The (R)evolution in Book Composition . . . IV”,

the time-shared computer, and editing of displayed 1964, p. 69.)

commands is possible. As the user's conversation “. "Kroemer (1965) . . . arranged the keys in two

with the catalog system progresses, certain data

supplied by the computer may be stored locally for separate but symmetrical groups, one for each hand. Each group consists of three curved rows of five

future reference, edited as required, and eventually keys. The form of the curve corresponds to that of

printed in hard-copy form." (Haring, 1968, p. 37). the fingers and the possible movements of the 4.27 “On the hardware side the picture seems to individual fingers. The two space bars for the be much brighter, at least in terms of providing

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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 large

screen 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 interro

gation 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,

a 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

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, however, exhibit serious 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).

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