Then, as Wooster comments: "Radically different types of computers may well be needed. At present, the best way of building these seems to be through the creation of logical structures tending more and more in the direction of distributed logic nets, wherein vast numbers of processes occur simultaneously in various parts of the structure. Right now, the best building blocks for such systems seem to be multifunctional microprogramable logic elements." (1961, p. 21).

Increasing complexity of central processor design is indicated by developments in advanced hardware technologies; 5.82 while increasing flexibility is dictated by dynamic reconfiguration requirements.5.83 Modularity is an important consideration.5.84 The critically challenging, interacting problems of both design, programming and utilization of multiprocessors and of parallel processing are emphasized by Brooks (1965), Amdahl (1965), Burkhardt (1965), and Opler (1965), among others. Thus: "The use of multicomputers implies intercommunication, with the associated implications of interconnection, reconfiguration and interlocking.” (Amdahl, 1965, p. 38).

5.2.2. Parallel Processing and Multiprocessors The possibilities for the use of parallel processing techniques should receive increased R & D attention. Such techniques may be used to carry out data transfers asynchronously with respect to the processing operations,5.85 to provide analyses necessary to convert sequential processing programs into parallel-path programs,5.86 or to make allocations of system resources more efficiently because constraints on the sequence in which processing operations are executed can be relaxed.5.87 Applications to the area of pattern recognition and classification research and to other array processing operations are obvious.5.88

However, there are problems of effective use of parallel processing capabilities. Some examples of the discernible difficulties with respect to current parallel-processing research and development efforts have been noted in the literature as follows: (1) "Multiprogrammed processors will require more explicit parallel control statements in languages than now occur." (Perlis, 1965, p. 189.)

(2) "Much additional effort will have to be put into optimizing compilers for the parallel processors that may dominate the computer scene of the future." (Fernbach, 1965, p. 84). (3) "Computers with parallel processing capabilities are seldom used to full advantage.' (Opler, 1965, p. 306).

on the sparcity of attempts made to date on the potentials of parallel processing in programs for many problems. He states further that while the tasks of segmenting the problem itself for parallel processing attack are formidable, "they must be undertaken to establish whether the future development lies in the area of parallel processing or not. "5.90 Then there is need for judicious intermixtures of parallel and sequential processing techniques in specific design, programming, or application situations.5.91

Parallel processing potentials are also closely related to, and may be interwoven with, multiprocessing systems which involve: "The simultaneous operation of two or more independent computers executing more-or-less independent programs, with access to each other's internal memories . (Riley, 1965, p. 74). In particular, the Solomon Computer and Holland Machine concepts may be noted.5.92 For another example, increasing parallelism of operation of a multiple access processing system has been investigated at the Argonne National Laboratory in terms of an "Intrinsic Multiprocessing" technique consisting of n time-phased "virtual" machines which time-share very high speed execution hardware (Aschenbrenner et al., 1967), while ILLIAC III has been designed for parallel processing of pictorial data.5.93

5.2.3. Hardware-Software Interdependence The earlier dichotomy as between "hardware" and "software" considerations is beginning to yield, not only to the increasing interdependence of the two factors in many information processing application requirements, but also to technological developments in "firmware" (in effect, wired-in microprogramming 5.94) and to growing recognition of the critical importance of more precise and comprehensive "brainware" in systems planning, design, specification, and implementation.5.95

Is it currently possible to separate computer and storage system design considerations from those of programming language design and of programmed executive control? Several experts testify that, if it is still possible today, it will soon be so no longer.5.96 It can be quite clearly seen that the areas of computer theory and program design are becoming increasingly interdependent with those of adequate programming languages, "software", and usertolerance levels. At the same time, new possibilities for multicommunicator, multiprocessor, and multiuser networks are increasingly coming to the fore. The growing interdependence is stressed, for example, by Schultz (1967),5.97 and by Lock (1965) who notes the strongly increasing influence of multiprogrammed, on-line systems upon the organization of the storage facilities. Scarrott (1965, p. 137) for another example, insists that "the problems of designing and using multilevel storage systems are in a real sense central to the design of computing systems.'

Thus, "as we enter an era of bigger and more complex systems some new requirements are coming to be of major importance.

Will we be able to minimize the program handling by proper allocation to primary, e.g., core, or secondary, e.g., drum or disk, storage?

● Will we be able to incorporate changes to the functional operation of the system?

Will we be able to modify the system to accommodate new or additional hardware?

• Will we be able to add a completely new function to an already operating system?" (Perry, 1965, p. 243).

In the next section, therefore, we will consider some of the advanced hardware developments before discussing such overall system design considerations as debugging, on-line instrumentation and diagnosis, and simulation.

Certain obvious overall system design requirements have to do with the further extensive development and application of advanced hardware technologies, especially opto-electronics generally (and lasers and holography in particular), with integrated circuit techniques, and with improved high-density storage media.

Recurrent themes in current progress toward very-high-speed, computer-controlled

access to

primary, secondary and auxiliary storage banks, from the standpoint of hardware technology, include the questions of matching rates of data-and/orinstruction access to those of internal processing cycles, and of the prospects for integrated circuit and batch fabrication advantages in design and construction.

These new technologies may also be combined in various ways. For example, Lockheed Electronics has been using deflected laser beams to scan photochromic planes very rapidly and very accurately,6.1 laser and holographic techniques are conjoined in equipment designed to photograph fog phenomena in three dimensions,6.2 and it has been reported that "laser devices show promise of very fast switching which together with optical interconnections could provide digital circuits that are faster than electronic circuits." (Reimann, 1965, p. 247).

6.1. Lasers, Photochromics, Holography, and Other Optoelectronic Techniques

New hardware developments that are technically promising in terms of the long range research and development necessary to support future improvements in information processing and handling systems include the development of special laser techniques for switching, storage, and other purposes, and the possible use of holograms or kinoforms for 3-dimensional pattern recognition and storage.

6.1.1. Laser Technology

Writing in 1965, Baker and Rugari have pointed out that "a wide variety of lasers have been discovered and developed since the first laser device was operated five years ago. 6.3 Lasers can be classed

into three basic types: solid-state, semiconductor, and gaseous. Typical examples are the ruby solidstate laser, gallium arsenide semiconductor laser, and the neon-helium gas laser." (1966, p. 38).

Certainly, lasers, whether of the gas, fluorescent crystal, or semiconductor type,6.4 are finding many new possibilities of application in computer, communication, and information processing systems.6.5 As sources of illumination they can provide greater display efficiency 6.6 and greater resolution with respect to display systems involving lightbeam deflection techniques (Soref and McMahon, 1965, p. 60),6.7 and they provide an effective aid to the boundary and contrast enhancement techniques for image processing developed at the National Physical Laboratory at Teddington, England. More specifically, this technology promises new developments in space communications,6.8 in memory construction and design,6.9 in the development of analytical techniques such as Raman spectroscopy and photomicroscopy,6.10 in the identification of fingerprints,6.11 in quantization of high resolution photographs 6.12 and in the use of holograms for collection, storage, and regeneration of two- and three-dimensional data.6.13

6.18

Small, very high-speed memories may be driven by laser beams,6.14 and laser components contribute to the design of "all-optical" computers 6.15 and computer circuits and components." 6.16 Laser inscribing techniques are being investigated for such applications as large screen real-time displays,6.17 and for highly compressed data recording, for example, at Precision Instrument Company. As of March 1969, it could be reported that orders had been placed for UNICON systems by Pan American Petroleum Corporation, and were under consideration by several other organizations, including U.S. Government agencies.6.19 In particular, the National Archives and Records Service has been studying the possibilities of converting present magnetic tape storage to this system.6.20

Investigations of future technical feasibility of using laser devices for high speed data storage and/ or processing have thus been complemented by exploration of possibilities for recording onto very large capacity storage media as also in developments at Honeywell,6.21 at the Itek Corporation,6.22

and at RCA,6.23 an IBM system designed for and now in operation at the Army Electronics Command as well as IBM developments in variable frequency lasers,6.24 and a recording system from Kodak that uses fine-grained photographic media, diffraction grating patterns, and laser light sources.6.25 Holographic techniques may also be applied to the development of associative memories with possible analogies to human memory-recall systems.6.26

Kump and Chang (1966) describe a thermostrictive recording mechanism effected on uniaxial Permalloy films by the application of a local stress induced by either a laser or an electron beam, promising large capacity memories of better than 106 bits per square inch storage efficiency.6.27 Then there are combined optical and film techniques for digital as well as image or analog recording and storage. Specific examples include IBM photo-chip developments,6.28 thermal recording developments at the NCR research laboratories,6.29 Precision Instrument's UNICON System,6.30 and, in general, the area of photochromic storage technology.

Areas of continuing R & D concern with respect to laser communications possibilities include questions of modulation and transmission,6.31 acquisition and tracking problems,6.32 isolation from 6.33 conditions,6 atmospheric interferrence and possibilities for controlled atmosphere systems.6.34

Vollmer (1967) notes that an experimental shortrange laser communication system has narrow beam width with significant advantages for privacy. In particular, "operation at 9020 Å enhances this privacy by virtue of its invisibility." (p. 67.) Some examples of the experimental use of lasers for communications purposes were given in an earlier report in this series,6 6.35 and it was noted that the most successful ventures to date have been at opposite ends of the distance spectrum.6.36 However, laser scanning techniques combined with other means of communication may offer important gains in high-resolution facsimile transmission. For example, a system developed by CBS Laboratories uses a laser beam to scan photographic film, convert to video signals, and transmit, via satellite, military reconnaissance pictures from Viet Nam to Washington.6.37

Continuing requirements for further developments in the application of lasers in display systems involve, for example, efforts directed toward less expensive high quality semiconductor lasers 6.38 and toward solving problems of deflection, modulation, and focusing.6.39 Kesselman suggests that results to date in terms of laser displays are inconclusive and that practical applications are not likely in the near future (1967, p. 167). As in the case of laser versus electron beam display,6.40 the absence of requirements for vacuum techniques favors the eventual use of laser rather than electron beam techniques in many high density data storage recording applications.6.41

6.1.2. Photochromic Media and Techniques

By definition, photochromic (or phototropic) compounds exhibit reversible effects or color changes, resulting from exposure to radiant energy in the visible or near visible portions of the spectrum.6.42 Such media give excellent resolution and reduction characteristics, and because of the reversibility property, they can theoretically be erased and rewritten repeatedly,6.43 although a continuing area of R & D concern is that of problems of fatigue.6.44 They also enable storage of images with a wide range of gray scale.6.45 Such materials have been known for at least a hundred years or more (Smith, 1966). In fact, as Smith suggests, they may have provided the means for achieving the world's first "wrist-watch." 6.46

Tauber and Myers (1962) and Hanlon et al. (1965) offer summaries of NCR efforts to provide commercial applicability to photochromic recording techniques for large-capacity micro-image storage files.6.47 A British example of application is the Technical Information on Microfilm Service.6.48

A less favorable characteristic of the photochromic material appears in the case of storage files - the permanency of recording depends on ambient temperature, ranging from only a few nours at normal room temperatures to perhaps several years under rigid temperature controls.6.49 Therefore, for mass and archival storage, the NCR system involves transfer from the photochromic images to a high-resolution photographic emulsion for permanent files. 6.50 The remaining advantages are two-fold. First, the reduction is impressive: 1,400 pages of the text of the Bible on an approximately 2" x 2" film chip is the widely demonstrated example (Fig. 2). Secondly, 'spot' erasure and rewriting provides an important inspection and error correction capability. It is claimed that: "Instantaneous imagery followed by immediate inspection permits the production of essentially 'errorless' masters for the first time". (Hanlon et al., 1965, p. 10).

In the area of internal memory and switching design, Reich and Dorion (1965) report of the photochromic techniques that: "The photochromic medium has extremely large storage capacity latently available in physically small dimensions. The basic photochromic switches are the molecules themselves. . . Photochromic media can be employed for many write-erase-rewrite cycles and give almost nondestructive read . . . Appropriate photochromic systems can retain stored data without power consumption . . . The memory can probably be designed to be stored for quite a long time." (p. 572) 6.51

A photochromic medium in the form of transparent silicate glass containing silver halide particles has been suggested for such applications as erasable memories, displays for air traffic control operations, and optical transmission systems.6.5

In addition, it is to be noted that photochromic films may be activated by CRT phosphors for use in information display systems (Dorion et al., 1966)6.53 and may also be used for real-time target tracking.6.54 Recent developments suggest the use of photochromics for digital data storage.6.55

Finally, the properties of photochromic materials might be used for improved performance of holographic recording, reconstruction and display systems.6.56 Thus, "the use of self-developing photochromic devices in the place of the photographic plate would enhance the value of wavefront reconstruction microscope by permitting nearly real-time operation and eliminating the chemical development process." (Leith et al., 1965, p. 156).

6.1.3. Holographic Techniques

Holography is a new information processing technique, but it is, in fact, highly illustrative of

needs for truly long-range R & D planning in many areas of computer and information sciences and technology, since it is by no means a recent area of investigation, the principles having been announced by Gabor as early as 1948.6.57 The basic holographic phenomena are described by Cutrona (1965, p. 89) as follows: "A hologram is produced by recording on photographic film the interference pattern resulting from the illumination of some object with a wavefront from the same source".6.58

Leith et al. (1965, p. 151) point out further that "by combining conventional wavefront reconstruction techniques with interferometry, it has been possible to produce holograms from which highquality reconstructions can be obtained. These reconstructions bear close likeness to the original object, complete with three-dimensional characteristics. The object can be a transparency, or it can be a solid, three-dimensional object" 6.59

Armstrong (1965) emphasizes that, in general, no lenses are required and the reconstructed image can be magnified or demagnified as desired.6.60

As of early 1969, however, the question has been raised that holograms may be already outdated.6.61 A new wavefront reconstruction device - the kinoform-is a computer-generated device intended to provide a reconstructed three-dimensional image of various objects with greater efficiency than is available with holographic procedures (Lesem et al., 1969),6.62

In addition to the use of holographic techniques for three-dimensional image storage and recall (including rotation 6.63), these techniques are also being explored for bandwidth compression in pictorial data storage 6.64 the production of highly magnified images,6.65 and other novel applications.6.66 In particular, it has been claimed that holographic techniques offer a new potential for high-quality-image capture in regions of the electromagnetic spectrum extending beyond those that have been achieved by optical recording techniques in the the region of visible light.6.67

Then it has been reported that "General Electric's Advanced Development Laboratories, Schenectady, build a laser holograph reader - a device capable of reading characters in several ways. It can detect a single object out of many without scanning, or if scanning is used, can recognize up to 100 different characters. The holographic reader is said to show wide tolerance for variations in type font and is expected to find applications in the computer field." (Veaner, 1966, p. 208.)

Laser and holographic techniques in combination are also being investigated for high density digital data storage, for example, at the Bell Telephone Laboratories, 6.68 at Carson Laboratories,6.69 and at IBM.6.70

Some special areas where advanced optoelectronic techniques and improved materials or storage media continue to be needed include "certain operations, such as two-dimensional spatial filtering (that) can be readily accomplished, in principle, with coherent light optics. Problems under consideration include: the effect of film-grain noise on the performance of a coherent optical system; the relation of film thickness and exposure; techniques for the making of spatial filters; and the effect on the reconstructed picture of various operations (such as sampling, quantization, noise addition) upon the hologram. (Quarterly Progress Report No. 80, Research Laboratory for Electronics, M.I.T., 221 (1966).)

McCamy (1967) reports recent extension of previous R & D investigations into fading and aging blemishes in conventional microforms to the effect of formation of such blemishes on information stored by means of holograms. It is to be noted further that certain types of holograms have an important immunity to dust and scratches.6.71

Possibilities for a holographic read-only store are under investigation at IBM (Gamblin, 1968), RCA (Viklomerson et al., 1968), and at the U.S. Army

Electronics Command, Fort Monmouth. In particular, "it is intended that a hologram of a binary data array would constitute the card-like removable media. Upon insertion into the memory read unit, the hologram would continuously focus a real image on the data onto a photodetector matrix. Such an arrangement can permit electronic random access to the information within the array while eliminating the stringent optical requirements on the detectors involved." (Chapman and Fisher, 1967, p. 372),6.72 Other R & D possibilities of interest include experimentation with acoustic 6.73 and computer-generated holograms.6.74 The computer generation of holographic or kinoform recordings is thus another development in this area of advanced technology. For example, digital holograms may be generated by computer simulation of wave fronts that would emanate from particular optical elements arranged in specific geometrical relationships (Hirsch et al., 1968).6.75 An interesting area of investigation is that of computer synthesis of holograms of three-dimensional objects which do not, in fact, physically exist.6.76

6.1.4. Other Optoelectronic Considerations

In general, it is emphasized that increasing interest has been evident in the use of optoelectronic techniques for both computer and memory design for a wide variety of reasons. Scarrott (1965) and Chapman and Fisher (1967) point to the high densities achievable with photographic media. 6.77 Reich and Dorion (1965) suggests a photochromic film memory plane, 2" x 2", with 645 subarrays individually accessible and a total capacity, assuming only 50 percent utilization of the film area, of better than 12 million bits.6.78 Potentially, then, many of these techniques promise significant advances in data storage, in logic and processing circuitry, in alternative communications means, in computing or access speed, and in data collection with respect to two- and three-dimensional object representation, including spatial filtering.6.79

Bonin and Baird (1965, p. 100) list other applications of optoelectronic techniques for tape and card readers, position indicators, and recognition equip ment. In addition, important new areas will include use in communication and transmission systems. Here it is noted that optical techniques as applied to advanced communication systems planning relate also to continuing theoretical investigations. Thus, "preliminary studies of communication systems employing optical frequencies have indicated three topics to which the concepts and techniques of modern communication theory may most profitably by addressed. They are (i) the import of quantum electrodynamics for the characteristics of efficient communication systems, (ii) the relevant description of device noise as it affects the performance of communication systems, and (iii) the statistical characterization of the atmosphere as a propagation channel at optical frequencies." (Quarterly Progress