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 7 
 
 THE MINICOMPUTER: AN EDUCATIONAL TOOL 
 
 by 
 
 LARRY GENE MARSHALL 
 
 February, 1971 
 
THE MINICOMPUTER: AN EDUCATIONAL TOOL 
 
 BY 
 
 LARRY GENE MARSHALL 
 A.B., Fort Hays Kansas State College, 1959 
 
 THESIS 
 
 Submitted in partial fulfillment of the requirements 
 for the degree of Master of Science in Computer Science 
 in the Graduate College of the 
 University of Illinois at Urbana-Champaign, 1971 
 
 Urbana, Illinois 
 
Ill 
 
 ACKNOWLEDGEMENT 
 
 The author would like to express his deepest gratitude to Professor 
 Donald B. Gillies for suggesting this thesis topic. His encouragement and 
 good advice have led this work to the successful completion. Additional 
 thanks go to Mr. Clifford Carter for his cooperation and suggestions. Further- 
 more, I am indebted to Mrs. Linda Bridges without whose excellent job of 
 typing, the final form would have never come out. Thanks also are extended 
 to Miss Bonnie Malcor, Mrs. Glenna Ganow, Miss Judy Knox, Miss Joyce Vaughn, 
 Mrs. Diana Mercer, and Miss Sue Cook who contributed in typing. And most 
 especially, I am indebted to my wife, Nada, for her patience, understanding, 
 and encouragement. 
 
 My special thanks are extended also to the Offset Department and 
 Dennis Reed for giving my thesis special attention on such very short notice. 
 
IV 
 
 TABLE OF CONTENTS 
 
 Page 
 
 1. INTRODUCTION 1 
 
 1 . 1 Introduction to Long-Range Planning 1 
 
 1.2 Summary of Educational Guidelines 1 
 
 1 . 3 Comments on Educational Guidelines 3 
 
 2. ANOTHER INSTRUCTIONAL TOOL 1+ 
 
 2.1 Goals - Individuality 5 
 
 2.2 Cost Versus Value - Goal Dependent 6 
 
 2 . 3 Maintenance Preparation - Reliability 7 
 
 3. JUSTIFICATION FOR THE USE OF COMPUTERS 10 
 
 3 • 1 Problems Requiring a Solution 11 
 
 3 • 2 Needs of the System Fulfilled 12 
 
 k. INSTRUCTIONAL USE l6 
 
 k • 1 Types of Use 17 
 
 k . 2 Centralization Versus Decentralization 18 
 
 k.3 Computer Utility 19 
 
 5. COMPUTER AFFECTED PROBLEMS IN EDUCATION 21 
 
 5.1 The Challenge of the Computer 21 
 
 5-2 Growth Impeded ? 2k 
 
 5»3 A Testimony of Success 25 
 

V 
 
 Page 
 
 6. STRUCTURE AND CONTROL OF THE COMPUTER FACILITIES 27 
 
 6.1 Information Dissemination 28 
 
 6.2 Separate and Unequal 28 
 
 6.3 The Central Facility 29 
 
 6.4 Interface Compatibility 30 
 
 7 . THE COMPUTER AS AN EDUCATIONAL TOOL 31 
 
 7 • 1 The Teacher's Responsibility 32 
 
 7.2 The Student Stimulated 33 
 
 7 • 3 Programmed Course Work 34 
 
 7 - 4 The Team: Student-Teacher-Machine 36 
 
 7 - 5 The Student /Teacher 's Records Keeper 37 
 
 8. THE MINICOMPUTER 40 
 
 8. 1 The Cost/Performance Ratio: Reduced 45 
 
 8 . 2 The Minicomputer Defined 46 
 
 8 . 3 Minicomputers — Contrasted and Compared 47 
 
 8.3-1 Minicomputer Description 52 
 
 3-1-1 Block Diagram 52 
 
 3-1.2 Memory 53 
 
 3-1-3 Word and Instruction Length 55 
 
 3-1-4 Addressing 56 
 
 3-1-5 Paging 57 
 
 8.3.2 Minicomputer Organization 58 
 
 3-2-1 Registers Identified 60 
 
 8-3-2.1.1 Storage Address and Storage 
 
 Buffer Registers 60 
 
 8-3-2.1.2 Arithmetic Register 60 
 
 8-3-2.1.3 Carry Register 60 
 
 8.3-2.1.4 Auxiliary Register 60 
 
 8.3-2.2 Methods of i/O Transfer 60 
 
 8.3'2.2.1 P rogrammed Data Transfer 6l 
 
 8.3-2.2.2 Direct Memory Access 6l 
 
 8.3.2.2.3 Multiplexor i/p Channel 62 
 
vi 
 
 Page 
 
 8.3-2.3 Interrupt Systems 62 
 
 8. 3*2. 3-1 Single -Level Interrupts 63 
 
 8.3-2.3.2 Multiple Level Interrupt System 63 
 
 Q.k The Minicomputer's Peripherals 63 
 
 8.4.1 General 63 
 
 9- PERIPHERALS 65 
 
 9. 1 General Comparisons 65 
 
 9 • 2 0(C/M)R or Sensing 68 
 
 9 • 3 Graphic Processing 69 
 
 10. REMARKS 73 
 
 10 . 1 Assumptions, Delivery, and Credibility 73 
 
 10 . 2 Reflections from Logicon 2+2 77 
 
 11. WHERE FROM HERE 80 
 
 11 . 1 Microprogramming 80 
 
 11.2 Applications 82 
 
 11.3 Advantages of Microprogramming Performance in System 
 Applications 83 
 
 LIST OF REFERENCES 86 
 
VI 1 
 
 LIST OF TABLES 
 TABLE Page 
 
 1 Cost/Performance Standardized to the 1970 Edition, Auerbach 
 
 Computer Characteristics Digest ^2-^4 
 
 2 Minicomputer Characteristics ^9-51 
 
viii 
 
 LIST OF FIGUEES 
 
 Figure Page 
 
 1. A Digital Computer Interfaces with Man and the World 52 
 
 2. Basic Minicomputer 5^ 
 
 j5« The Organization of a Typical Minicomputer 59 
 
 h. Total Cost/1000 Bytes of Off-Line Data Storage vs. Amount of Off- 
 
 Line Storage for Minicomputer i/o 66 
 
 5. Logicon 2+2 System Logical Structure 79 
 
 6. Microprogrammed Control Unit Organization 8l 
 
1. INTRODUCTION 
 
 1.1 Introduction to Long-Range Planning 
 
 This study can be likened to a journey. The traveler prior to his 
 departure is well advised to study his guide books before launching any adventure. 
 Our guidebook for this educational exploration is: PRELIMINARY REPORT OF LONG- 
 RANGE PLANNING COMMITTEE FOR THE URBANA- CHAMPAIGN CAMPUS, THE UNIVERSITY OF 
 ILLINOIS, URBANA- CHAMPAIGN CAMPUS, OFFICE OF THE VICE CHANCELLOR FOR ACADEMIC 
 AFFAIRS, FEBRUARY, 1970. 
 
 In Section 1.2 we summarize relevant portions of its contents and in 
 Section 1.3 we comment briefly on these guidelines. 
 
 1.2 Summary of Educational Guidelines 
 
 In this report, the committee stated that the chief functions of the 
 University, as the state's educational system developed, were the following: 
 
 1. Teaching, research and scholarly and creative activity in the 
 fundamental fields of learning 
 
 2. Teaching and research in professional and occupational areas 
 closely dependent on the fundamental fields of learning 
 
 3« Liberal education of able young men and women who do not intend 
 to become highly trained specialists and, to the extent possible, 
 of students aiming toward specialized or professional training 
 
 k. Vocational training in fields which are clearly of substantial 
 
 and wide importance to the state and nation, especially those which 
 require four-year programs including sound preparation in the 
 fundamental fields of learning and which the University is uniquely 
 or best fitted to provide 
 
 The fundamental fields of learning were defined as mathematics, the 
 
 biological and physical sciences, the humanities, the fine arts, and social 
 
sciences. These were defined as fundamental "not only because they have long 
 been studied for their own sake but also because they underlie most fields of 
 applied knowledge." In the fundamental fields, it was contended, basic research 
 is the source of every advance in the applied fields. 
 
 Predictions of the growth in the size of the college-age population, 
 and the proportion of that population demanding college education through the 
 most advanced degrees, are conservatively estimated to increase so that the 
 need to provide college education to some 60 to 65 percent more students in 1980 
 than in 1969. Further, it is likely that the proportion of Illinois students 
 who are candidates for Master's and Ph.D. degrees will increase more rapidly 
 than those enrolled for the baccaluareate . 
 
 At the present rate of technological and scientific development, the 
 store of knowledge doubles every ten years. Not only must students of the future 
 learn more, but teachers themselves must be continuously learning to keep their 
 knowledge of their subject matter from becoming obsolete. The capacity of 
 universities to provide an environment in which their teachers can learn will be 
 a benchmark in differentiating the great from the ordinary university of the 
 future. That university which provides its academic staff with time and 
 facilities for scholarship and for relevant basic and applied research will be 
 tomorrow's academic pacemaker. 
 
 "Our primary and foremost function will continue to be education — the 
 educating of research scholars, of 'teachers of teachers', and of professional 
 practitioners . " 
 
 It is the intent of the Urb ana -Champaign campus to provide leadership 
 in the effective pursuit of the following objectives: 
 
1. the development of human resources through education 
 
 2. the expansion and dissemination of knowledge through research 
 and teaching 
 
 l.J Comments on Educational Guidelines 
 
 Our opinion is that the above guidelines are well designed, make sense 
 for the Urbana-Champaign campus, and might very well apply to most educational 
 institutions. We propose to apply them throughout this thesis. 
 
2. ANOTHER INSTRUCTIONAL TOOL 
 
 Enter the computer. The promise seems immense. Like books or tutors, 
 computers can serve any goal. They are indifferent to how the processes they 
 apply are created. The man-made programs that control computers can embody 
 universal or particular goals; they can either be mass-produced or hand-tailored 
 on the spot. Like a book, a computer can perform for either a group or a lone 
 individual. 
 
 Stored-program technology endows any one computer with great flex- 
 ability. It is at least as general as a blackboard. Multiple access and 
 communication techniques promise parallelism, that is, simultaneous availability 
 to many students, and also easy physical accessibility. A computer itself is 
 potentially an excellent tool for scheduling anything, including itself. Like 
 good tutors, who can marshal resources beyond their own, computers can marshal 
 most other educational devices and make them perform at their command. 
 Computers have given other devices — slide projectors and tape recorders — renew- 
 ed dignity as part of the world of technological innovation. 
 
 There are many aspects of the educational scene which might benefit 
 from the application of the rules of competition as it operates in the system 
 of free enterprise. 
 
 We must encourage as much diversity as possible — as many paths, as 
 many different outlooks, as many different experiments, as many different 
 initiatives as we can afford once the demands of education have been balanced 
 against those of other needs or our society. 
 
2.1 Goals - Individuality 
 
 Individuality is a recurrent theme in educational planning. It is 
 responsible for providing: 
 
 1. A program of studies that provide a meaningful sequence of 
 subjects for each student according to his abilities, needs, 
 and objectives including a core of common learning for all 
 students that should assure an adequate base of general 
 education 
 
 2. Counseling services that -will achieve for the student his 
 desire to achieve for himself these merits 
 
 Goals of education may be either universal or particular. A universal 
 goal is literacy; and we would like to achieve it in practice. Yet, we do not 
 require that all play the piano. De facto national standards are established 
 by the College Board exam, yet there is no insistence that all pass the exam 
 required of a certified public accountant. 
 
 The balance between uniformity and deviation has deep social con- 
 sequences. How much uniformity does this society need for safety? How much 
 deviation does this society require for progress? 
 
 Educational technology cannot be equated with inert devices such as 
 the computer. They are only the kit of tools that people may use in a process 
 to achieve some human end. The kit includes physical devices, "hardware" in the 
 jargon, but it is useless without intellectual content, or "software", which 
 animates the tools and gives them meaning precisely in the way that meaningful 
 printed words differentiate a book from a bound collection of blank pages. The 
 choice of tools appropriate to a purpose and their organization by and with 
 people into a harmoneous, well-balanced process that fits the stated purpose is 
 an important part of the job of systems designers. Defining the purpose is 
 
policy making and not systems' design, although in practice means and ends are 
 never independent of one another. 
 
 2.2 Cost Versus Value - Goal Dependent 
 
 I feel it is necessary to clarify the cost verses value issue. Cost 
 is the more easily defined, for purchase or rental of equipment is a true cost. 
 It may he presented more complexly, however, if the direct expenses are amortized, 
 presented, or hidden in many other ways depending on the methods of accounting. 
 
 Value is goal dependent. The extremes are: to consider on the one 
 hand only dollar values, such as teachers' salaries or pupils' equipment and/ or 
 lifetime earnings, or on the other hand, to always place human values and the 
 human spirit over system efficiency. Let us review some factors that, though 
 not logically independent of one another, are sufficiently distinct to he 
 considered in isolation. Flexibility or adaptability is the ability of man, 
 machine, or organization to meet the needs of the moment. People have varying 
 degrees of flexibility. Organizations that encourage individual initiative 
 are more flexible than those that work solely by the book. Brick walls, folding 
 partitions, screens, and movable furniture are increasingly flexible ways of 
 partitioning a room. The value of each depends upon whether changes need to 
 be made in years, hours, minutes, or seconds. The choice of course also depends 
 on cost, fire retardation, noise resistance, etc. Now a blank piece of paper 
 and a chalkboard can both be written on; what is written on one can be written 
 on the other. They possess great generality for most anything can be written on 
 either. Since the board can be more readily erased by the line, word, or letter, 
 and have a ready insertion, it is more flexible. 
 
Parallelism is the simultaneous availability of multiple instances of a 
 given resource. Because a roomful of students during an exam ■writing on his own 
 paper is common, paper is more parallel as a resource than the chalkboard which 
 will accommodate only four or five pupils. The amount of a resource, say a ream 
 of paper, which could be easily distributed, or a "flexible" stenographer's pad 
 used only by the secretary, is important, as is physical accessibility. 
 
 The ease of getting at a resource usually depends on two barriers : 
 the distant supply room — a physical restraint — and management inventory control 
 where "X units will be available for the month of April". Organizations' audio- 
 visuals are usually stored remotely to normal user location. Obviously, 
 parallelism is low. If there are many calls (demand) for device Q, scheduling 
 may develop into a serious problem. 
 
 2.3 Maintenance Preparation - Reliability 
 
 Reliability and maintenance are as hand-in-glove. Light bulbs burn 
 out and need to be replaced. The bulb is "expected" to burn (reliable) for 
 twenty-five hours in a certain projector. The machine will be returned for 
 maintenance — a five minute bulb replacing project — one day after it burns out. 
 The machine will be in the shop two days. Highly reliable bulbs might signal a 
 2lt--l/lt- hour-use shop rotational scheduling time sequence to the Department of 
 Maintenance, etc. Low reliability might bring a "bulb replacement class" so 
 that an extra bulb with the machine might easily be replaced. Preventive 
 maintenance may be the running of a fan an extra five minutes so that the 
 filament cools to room temperature. 
 
With the shift from the large to the smaller user, or if you will, 
 from the device costing $1, 000 . 00/month rental down to $100.00/month, if 
 budgeted service expenditures are to remain at a fixed percentage of the monthly- 
 rental, the lower device must he ten times more reliable and ten times easier to 
 service (if ease and time of service can be directly related). Points to 
 consider include the number of moving parts, the total life cost, the number of 
 wear points, and the mean time to repair. Modularity expresses itself in ease 
 of serviceability and maintainability. 
 
 A non-pursued point: The consultants would be competent to trouble- 
 shoot outages, etc. Repair teams would be hired on a competitive basis from 
 within the organization (University of Illinois student/faculty c ommun ity) . 
 
 Device complexity affects training, operational use, and maintenance. 
 A chord organ is easier to learn to use--less hours of training are required 
 before playing for your enjoyment than the pipe or electronic theater organs. 
 Maintenance of the chord would be equivalent with the electronic theater organ 
 while maintenance crews for the pipe organ requires extensive training. 
 
 People should feel at ease and comfortable with whatever device they 
 are using. Not only does the operator desire the physical plant to fill this 
 need but also he wants to "feel" the assurance of what he considers the proper 
 response to his prepared stimuli. Clearly this is closely tied with reliability. 
 
 The standard 820 roll of film is useless to one with a 35MM camera. 
 The most impressive investment in programs tailored specifically to one computer 
 is worthless to the owner of another computer if that machine uses a different 
 "language". Now then, this stains of integration, the ability of two media to 
 work together. There is no system if, when given a textbook outlining 
 
experiments, there is none of the required equipment in the laboratory. A 
 book with blank pages — it contains nothing — cannot be a textbook; similarly, a 
 computer without programs is impressive but is equally worthless. 
 
10 
 
 3. JUSTIFICATION FOR THE USE OF COMPUTERS 
 
 Having considered many computer descriptors, let us see if, given the 
 
 technology, there is demand enough to justify its use. John R. Pierce, Executive 
 
 Director of Research, Communications Science Division, Bell Telephone Laboratory, 
 
 in the keynote address before the "Conference on Academic and Related Research 
 
 Programs in Computer Science" held at the State University of New York at 
 
 Stony Brook, June 5-8, 19^7, draws this conclusion as Chairman of a President's 
 
 Science Advisory Committee (1966): 
 
 "About 35$ of all college undergraduates were in courses of 
 study in which they could make substantial use of computers; 
 i.e., in many of their courses computers could help. About 
 k-0% were in courses of study in which they should make use 
 of the computer; i.e., they would make use of computers in 
 several of their courses but not the majority. The remain- 
 ing 25$ were in courses in which they should be exposed to 
 the computer and use it in one or more courses. THIS MEANS 
 THAT EVERYONE, IN UNDERGRADUATE EDUCATION SHOULD HAVE SOME 
 EXPOSURE TO THE COMPUTER AND A LARGE NUMBER OF STUDENTS 
 SHOULD USE IT EXTENSIVELY." (emphasis mine). 
 
 Under the assumption that computers are useful devices, which do something for 
 
 somebody, it is worth thinking and talking about the objectives of a computer 
 
 science education. 
 
 1. train effective workers who will be included in the force of some 
 hundreds of thousands of professional programmers and system 
 analysts who will be using digital computers 
 
 2. train computer designers or "system architects" 
 
 3- train people who will have extensive knowledge of computers and 
 those mathematical tools required to develop new ways of using the 
 computer. Equip them to recognize and to realize new and important 
 applications 
 
 h. train a select few in more theoretical aspects of computer science 
 and other relevant subjects so that by their research they can 
 further our understanding of effective procedures and the kind of 
 mental processes that can be accomplished by them 
 
11 
 
 3.1 Problems Requiring a Solution 
 
 Needs fall into three (3) categories: 
 
 1. personnel required by business, government, etc. 
 
 2. solutions to known problems such as how to devise a reliable 
 computer billing system or a reliable computer operating system 
 
 3- formulation and solution of such vague and little understood 
 problems as how to control computing systems and make them most 
 effective to extend human intellect and human freedom 
 
 To fill these needs, it is clear that three different type objective courses are 
 
 required: tool courses, liberal arts courses (including computer appreciation 
 
 courses), and the professional level computer science courses. Further, the 
 
 primary responsibility of the computer science faculty is an intellectural one 
 
 rather than a material or service responsibility; i.e., the primary responsibility 
 
 of the computer science department is education and the primary duty of the 
 
 computer center is service. 
 
 To be even more definitive, there are three types of users: novice, 
 
 technician, and programmer. A novice user creates no programs — he simply 
 
 supplies parameters to programs produced by others. Clerks, secretaries, 
 
 foremen, librarians, teachers, and managers qualify as novices. Using the system 
 
 on an interactive level, the notice programmer is restricted to functions such 
 
 as data entry, inquiry display, report generation, and function invocation. 
 
 The technician is a specialist in the intricate details of an occupation such 
 
 as engineering, finance, marketing, or manufacturing. He is a professional, but 
 
 not in programming. The programs he writes will solve his own problems or those 
 
 of a novice, although he is not aware of the system's hardware features or 
 
 capabilities. The kinds of functions used by the technician include file and 
 
 data-base definition, data entry, procedure definition, editing, and simple 
 
 program debugging. 
 
12 
 
 Professional programmers use PL/l, FORTRAN, assembly language, etc. 
 These users produce programs to meet the computational and data processing needs 
 of an organization. To accommodate their needs, the system provides facilities 
 to define hierarchies of named files; enter programs, data, and text into files; 
 translate source programs to form executable codes; test the resulting objective 
 programs, and insert them into the system to form new commands and programming 
 facilities. 
 
 This would not be complete if I neglect the definition of computer 
 
 science. "The study of computers is computer science," is a simple answer. It 
 
 is not quite so easy to answer some of the objections. These will be brushed 
 
 aside however in favor f two quotes on the subject: 
 
 PERLIS: Computer Science is the study of the design, analysis, 
 representation, and application of algorithms on 
 computers. All aspects of this study are like the layer- 
 ing of the onion. The study of algorithms is through the 
 use of algorithms, and each reveals others to study. 
 Computer Science has one goal: the understanding of the 
 organization and administration of information. 
 
 SLAMECKA: Let us suggest that "information" or, more precisely, 
 signals (signs) and symbols be considered as the 
 denominator of our field . . . Information is the one 
 component which occurs in the problem, in the solution 
 algorithm. The entire process of converting a problem, 
 from the first recognition of its existence to its 
 acceptable solution, can be viewed as a process of sign 
 or symbol manipulation. 
 
 3-2 Needs of the System Fulfilled 
 
 Although the number of computers in use in the University has increased 
 tremendously, the Rosser Report points out that the value of equipment installed 
 in universities remain between four and five percent of the value of equipment 
 installed in the whole country. The basic purpose of a university is to develop 
 
13 
 
 and to transfer knowledge. Eduction is an extracting process, a talent- 
 developing exertion. Eduction is a stimulative effort attempting to maximize 
 enlightenment from its sources wherever and whatever they may be. An eductor 
 cannot see what has not hove into his view BUT he is aware of the unknown or he 
 would not continue to reach for the sun. To the self -responsible: let the 
 reliance be solely on eduction; i.e., leave it to each person to turn his eye 
 to any or whatever light (s) he chooses. Permit him to be his own eductor; to 
 educe, drink in, infer from available data, as he pleases. 
 
 A major ingredient of knowledge is information, and therefore, one 
 would expect logically that the use of a computer should grow at a fast rate. It 
 is assumed that the growth in the use of computers is limited primarily by the 
 rate at which knowledge about computers diffuses both to specialists (those who 
 know how to make the computer produce output) and to non-specialists (those who 
 use the output of the computer) . If this conjecture is true, it follows from 
 the statistical data of the Rossier Report that the effective diffusion rate of 
 relevant knowledge is no greater in the university than it is in the rest of the 
 country. 
 
 It is worthwhile to emphasize that activities and decisions related to 
 computers are important to universities for at least two major reasons. The 
 university has a responsibility to provide the opportunity for the type of 
 atmosphere people need for successful careers in our society. With the increasing 
 number of computers installed, more people who are knowledgeable about computers 
 are needed. This includes not only education of specialists such as programmers 
 and computer scientists, but also education for those who will use the computer 
 as a tool. Secondly, with the ever increasing expenditures on education, there 
 
Ik 
 
 is an increasing emphasis on efficient use of resources and the computer can be 
 a powerful tool for more efficient use of resources. The 1971-2 expenditures 
 are estimated at $klk, 000, 000— up from $100,000,000 in 1968-9; less than 
 $25,000,000 was spent in 1965* If all of this money had been spent for computer 
 service on an IBM 709^-H at a cost of $300/hour of processing, about one minute 
 of computing was available for each undergraduate for the entire year. Or, if 
 you will about 5$ of the students could have received about twenty minutes of 
 processing per year. 
 
 Expenditures on computers are reaching significant size, becoming 
 increasingly more visible and will likely increase at a faster rate than other 
 expenditures. More on this matter will be discussed later. A point to ponder: 
 the cost of providing "adequate" computer systems is estimated at $60 per 
 student. This compares to the $50-$200 per student for college libraries and 
 $90 per chemistry student per year for a single chemistry laboratory course in a 
 four-year college. 
 
 Having expended a sum of money so as to have sufficient hardware 
 capability of the right kind available, effective use is now proving to be 
 difficult. The basic problem is in the paradoxical life cycle of a particular 
 computer configuration at an installational. When the computer is first acquired 
 it is not fully utilized because not enough problems are programmed for it. The 
 quality of the service to the user, "turnaround time", is good and the amount of 
 use increases rapidly as problems are programed and users become aware of the 
 service. As the computer nears saturation, "turnaround time" becomes worse. By 
 adding hardware components and by increasing the hours of operation the director 
 of the service center can prolong the user's tolerable turnaround time after 
 which the user will either seek other sources of computing or forget about it. 
 Now comes the next generation computer on the market and the cycle is repeated 
 
15 
 
 ■when it arrives. 
 
 A final point, the Mitre Corporation project costs for 197^ corresponds 
 to 5$ increase in today's education costs — an increase that could be offset by 
 adding only one student to an average class. 
 
16 
 
 k. INSTRUCTIONAL USE 
 
 As has been noted, in the field of scholarship and education, there 
 
 is hardly an area that is not now using digital computing. In the words of 
 
 the Pierce Report on Computers in Higher Education , "Computing increases 
 
 the quality and scope of education." In the book, INFORMATION , published 
 
 by Scientific American: 
 
 "The primary movement in contemporary applied science is 
 the assumption by machines of functions that until now 
 could be carried out only by human nervous systems. The 
 mechanization of functions that are too fast, too 
 dangerous, or too complicated and time consuming for 
 control by man, or that are unworthy of human effort 
 when machines can be made to do them, has created a 
 whole new technology — the technology of information." 
 
 Describing the pervasive effect of computers on our society, the "Pierce 
 
 Report" reflects: 
 
 "Indeed, it seems that the social and economic gains 
 which can be made through the use of computers and 
 computing may be limited chiefly by the availability 
 of people who are able to apply these tools in new and 
 useful ways. . ." 
 
 Having noted that "computers and computing are simultaneously an American 
 
 Resource and a challenge with a lead on the world. . .which gives as an 
 
 intellectual as well as an industrial advantage," the report continues: 
 
 "Students in college and universities must see for 
 themselves what a powerful tool computing is, and 
 learn to use it. No matter what his speciality, the 
 student must be given the opportunity of using computers 
 in learning and in doing, and the faculty member must 
 be able to use computers in teaching. Both the 
 individual's opportunities and the progress, well- 
 being, and stature of our society can be increased by 
 adequate computing facilities for our colleges and 
 universities." 
 
IT 
 
 k.l Types of Use 
 
 At least three distinct types of instructional uses of the computer lay 
 before us: 
 
 1. as a computational and information processing tool for the student 
 
 2. as a device for administering instructional materials and for 
 providing feedback to the student as he learns from those material- 
 computer-assisted instructions 
 
 3. as a laboratory instrument in the computer science curriculum 
 The computer enables the student to deal with realistic problems rather than 
 oversimplified models. By lessening the time spent in drudgery of problem solving 
 and in the analysis of data, it frees time for thought and insight. In part, the 
 old is made easier, but more time remains to reach for "new". 
 
 If we are to make any meaningful analysis of the uses of computers 
 in higher education, we must mention the types of service. The appropriate 
 unit in discussing computers is a unit of service involving not only hardware 
 time required, but also the programming language available, the specialized 
 hardware which must be attached to the general computer, the response time 
 of the overall facility to that user, etc. The computer facility user is 
 purchasing not machine muscle but a series of accesses to data and results. 
 
 As the total demand for computing is rapidly increasing, so also, 
 is the variety of demand for specific services. Thus, facility planning and 
 funding must take into account the consequences mentioned below of providing 
 new types of service. Note how these new service requirements may have severe 
 dislocation effects on the rest of the computer services system. 
 
 The incremental costs of providing the first units or a single unit 
 of service generally will be quite high. Lead times may be long due to heavy 
 
18 
 
 software investment required in providing the many new types of service. 
 This together with any specialized hardware involved, the provision of a 
 new service represents an additional large fixed cost whether there are 
 any users or not. 
 
 Each facility cannot provide every possible service. Decisions 
 as to which service to provide can imply significant differences both in 
 equipment and in their organization of the facility staff. For some types 
 of service, "stand-alone" equipment dedicated to a single use may be 
 appropriate . 
 
 k.2 Centralization Versus Decentralization 
 
 This comment on centralization: In any decentralized organization, 
 those able to look across several decentralized units from a centralized 
 location will see people "doing stupid things" - making bad decisions, 
 undertaking activities that duplicated efforts in other units, etc. This 
 is not always because the people are bad or stupid, but more often because 
 they are human, the future cannot be forecast perfectly, and the transfer 
 of information is neither complete nor free. There are two polar reactions 
 to this realization, and an infinite number of "combinations" of the poles: 
 
 1. strengthen the decentralized operation (better people, more money, 
 etc.) so that such mistakes become rarer 
 
 2. increase centralized direction and control, since the person on 
 top is less likely to make at least some of these mistakes (having 
 more complete information, supposedly) 
 
 With this in mind, let us turn to the commonly accepted; "the 
 
 power of a computer central processing unit goes up as the square of the 
 
 cost, " and thus there are economies of scale in terms of raw computing 
 
19 
 
 power at the CP. It is not always realized that a number of other factors 
 enter into the overall question of economics of scale, particularly when 
 applied to shared use of remote computing resources. Generally, there is 
 no data on a number of these factors, such as economies do not exist for 
 computer memories, and thus no way to make a sound judgement as to whether 
 economies of scale really exist in an actual operational situation or not. 
 Even discussions of the problem are few and far between. 
 
 k. 3 Computer Utility 
 
 The following list of factors which enter into the cost-effectiveness 
 trade-off of a centralized computer facility supplying remote service can 
 be found in the chapter entitled "Economic Considerations" in the book The 
 Challenge of the Computer Utility by Douglas Parkhill. While his discussion 
 is mainly oriented toward remote time- shared service, most of the factors 
 apply. The possible positive factors are: 
 
 1. fast response (that is, economically feasible fast response) 
 
 2. reduced user capital investment 
 
 3. better utilization of computer power (the blending of 
 disparate peak loads at different times) 
 
 h. better balance between user needs and user costs (since there 
 are a number of users possibly using different parts of the 
 system at once) 
 
 5- greater computer power for the user (a larger single machine 
 available when needed) 
 
 6. convenient access to broader set of data procedures 
 
 7. flexible system augmentation and modernization 
 
 8. reduced user maintenance and operating costs 
 
20 
 
 Negative factors listed include: 
 
 1. cost of communication facilities - this would include both 
 remote lines and the terminals needed at the remote 
 facilities 
 
 2. executive controller requirements; i.e., the overhead 
 necessary to provide a multiplicity of centralized services) 
 
 3. reliability and maintence problems (if the central system 
 goes down, nobody gets anything done) 
 
 k. system saturation problems 
 
 5. lost time due to "swapping" 
 
 A number of economists have pointed out the similarity between 
 computing facilities and the high capital investment, low marginal cost 
 operations of electric utilities. It is a common finding, for such an 
 industry or facility that at a given level of capacity it may not be possible 
 to recover all costs and at the same time use the capacity fully, even though 
 there is demand for the facility's service. 
 
 High quality service meaning, for the power company, no severely 
 reduced line voltages or outages and for the computer utility fast turn- 
 around at peak load times, costs money, and shows up as possible unused 
 capacity at non-peak-load times. Sometimes this capacity can be sold to 
 other networks of power companies or computer utilities, or can be used 
 for low priority operations : making aluminum or pumping water up into 
 storage lakes for power companies, or running background programs at reduced 
 rates for some users. The alternative to high quality service, namely partial 
 or total saturation is so wasteful of human time that it is almost never 
 cost-effective if the objective function being optimized includes a factor 
 for wasted human time. 
 
21 
 
 5. COMPUTER AFFECTED PROBLEMS IN EDUCATION 
 
 When man discovered how to convert the chemical energy stored 
 in fossil fuels into mechanical power, man's physical capabilities were 
 extended. Today man's mental self has been extended by the utilization 
 of the computer. A logic engine, a symbol manipulator, an information 
 processing machine, and a control device, the digital computer is an 
 invaluable tool in logical problem- solving, and with mechanical equipment, 
 the computer is a flexible and comprehensive task performer. 
 
 The responsibility of education extends beyond simply providing 
 appropriate instruction to those who are likely to make direct use of 
 computers; namely, it extends into the introduction of computer concepts as 
 a part of general education. This is in order to provide all students with 
 an understanding of what these devices are, what they can do, and how they 
 are affecting society. 
 
 5.1 The Challenge of the Computer 
 
 Education is challenged to use the computer as a teaching tool 
 and to reveal how its capabilities have been incorporated in the very 
 organization, structure and content of all current knowledge. Mathematics, 
 engineering and the sciences, while the most obvious, are not the only 
 academic fields directly affected by the computer's capability to process 
 information and to support the development of model systems simulating 
 segments of the environment. Languages studies are affected by techniques 
 of information storage and retrieval and new methods of exploring logical 
 
22 
 
 consistency. Applications to the managerial sciences make business, 
 economics, administration and commerce more viable, comprehensive and 
 intellectually challenging subjects. 
 
 The primary problem faced by education consists of determining 
 the relevance of the computer to each academic discipline: how can the 
 computer affect each discipline; develop curricula which incorporates the 
 computer as an integral part of their subject matter. 
 
 Another problem is developing operational methods which will 
 facilitate maximum ease of computer use at educational institutions. This 
 includes the development of computer languages geared to fast learning and 
 easy programming and the design of classroom facilities, course schedules, 
 and terminal devices for optimum computer access. 
 
 The final problem lies in providing computer services to classrooms 
 
 on a cost effective basis which will make computer-based curricula economically 
 
 feasible for educational institutions of all types and sizes. The question, 
 
 "Is it feasible?," is not just one of whether a job can be done by a computer, 
 
 rather, it is one of relative economics and requirements, contrasting various 
 
 ways of doing it (including improved non-machine methods.) Quoting Dr. 
 
 Peter G. Lykos, Computers In Education : 
 
 "There are two basic ways in which the computer can be 
 used. One consists of computer-assisted instruction in 
 which the student sits at a terminal and responds to 
 programmed course material. This requires that the 
 pedagogical technology be sufficiently advanced, that 
 "success" and "failure" are adequately adapted to each 
 student and that the concepts sequence for the subject 
 matter be optimally organized. It also requires that 
 the computer and computer terminal hardware and soft- 
 ware be sufficiently well developed and economically 
 feasible to support mass education. 
 
23 
 
 The second method involves the student addressing the 
 terminal as a stand-alone device in one of two distinct 
 modes of operation. In one operational mode, the 
 student confronts a problem, writes a program to work 
 through a solution to the problem, and then uses the 
 computer to implement the solution. In this case, the 
 student works out the solution himself and the computer 
 is simply a tool enabling him to solve the problem, 
 (if you will, the student is the teacher - the computer 
 the pupil) . 
 
 In the second mode, the computer contains an appli- 
 cation program and the student uses this program to 
 solve a problem. The program may simulate the 
 economy while students play the part of individual 
 companies attempting to maximize their profits. This 
 second mode has great potential today, but has not 
 been exploited (or recognized?) . It constitutes a 
 direct channel between the frontiers of knowledge and 
 the classroom. . ." 
 
 We suggest yet another way in which a student who is required to 
 use the computer benefits educationally. In his career he uses a number of 
 different computer languages, both low level and high. Many students use 
 four or five different ones, and some use well over twenty in their college 
 careers. Each language represents a different way of organizing data and 
 approaching problems. Just as travel is said to be broadening, and it is, 
 so with computer languages. 
 
 The computer touches everyone's life in a direct or indirect way. 
 The educated man of today must therefore be fully aware of the challenge and 
 problems posed by the computer. It is consequently one of the objectives to 
 establish guidelines to make computer- in- education an economically feasible, 
 technically viable, and academically effective reality. Achievement of this 
 goal is essential for man to realize his full intellectual capability. 
 
2k 
 
 5.2 Growth Impeded ? 
 
 In the MINUTES OF MEETING COMPUTER NETWORKS ADVISORY COMMITTEE, 
 June 15, I97O, STATE OF ILLINOIS BOARD OF HIGHER EDUCATION, Dr. Lykos points 
 to a number of problems impeding the growth of academic uses of the computer: 
 
 1. the main problem lies in discovering how computers can be used as 
 an integral part of curriculum 
 
 2. the developing computer languages geared to fast learning and easy 
 programming 
 
 3. the providing of economical services to eductional institutions so 
 that we can afford to use this tool 
 
 Dr. John Kemeny of Dartmouth states: 
 
 "At Dartmouth 80% of the freshman classes will have com- 
 pleted four significant exercises, in which they per- 
 sonally "debug" their own programs by the end of their 
 year. A significant number of students acquire the 
 habit of regular use." 
 
 Before introducing another quote of Dr. Kemeny, it should be clear that at 
 Dartmouth, they believe that learning to use a computer should be an essen- 
 tial part of a liberal education. The average graduate is almost sure to 
 need a computer in his work within this decade. Certainly they avail the 
 student the opportunity to use this powerful tool. Now Dr. Kemeny: 
 
 "After placing the computer at the fingertips of the 
 faculty, not only does the instructor use the computer 
 but also he feels free to ask his students to work 
 significant exercises and term projects on the computer. 
 He may be sure that his students know how to use a 
 computer, that they will be available, and that the 
 student will enjoy the assignment." 
 
 There are two probable reasons for their success; 
 
 1. an easy-to-use timesharing system 
 
 2. a simple language 
 
25 
 
 For the few readers requiring more background to the foregoing, let it he said 
 that batch-processing was designed to maximize the use of the computer for a large 
 number of significant problems— which are known to be correctly programmed. But 
 since man is not infallible, after waiting several hours to obtain the results, 
 probably with mistakes, the user must then make a correction, and resubmit 
 the problem. It may take two weeks of rather frustrating work until the 
 programmer succeeds. Yes, computer time may be optimized but not man's. 
 To handle many users with one machine, the time- sharing system was dis- 
 covered. 
 
 Most programmers have had moments of deep discouragement as they 
 drilled into their minds another language. The aim of producers of the 
 language was time: the language should be so simple as to be learned in 
 two or three one-hour meetings. After the initial meetings, the student 
 would learn from their own experience. (A language like FORTRAN or SNOBOL 
 requires that the user remember a large number of conventions and that 
 he specify a wide variety of options. This is too much. It is harder to 
 learn the language and the occasional users have to "relearn" the language 
 each time.) The language should encourage the novice; i.e., he should be 
 able to do something interesting on the computer during the first week 
 of the training periods . 
 
 5.3 A Testimony of Success 
 
 At Dartmouth, all freshmen who complete a year of math are 
 required to complete the freshman computer program. After the initial 
 introduction, each student has a teletype reserved for him for ^>/k of an 
 
26 
 
 hour per week, for nine weeks. He must write four assigned programs, debug 
 them, and pass the computer TEST on each program. "Experience shows that 
 students spend between one and two hours a week on their programs including 
 teletype time, and that 95$ of the programs are successfully completed." 
 
 Experience at Dartmouth indicates that the students find it con- 
 venient to use the computer for their homework and term assignments. They 
 use the computer to solve course problems without being told that they should 
 do so. (Students naturally try to find the easy way.) Dr. Kemeny notes 
 that the upper classman is often working two or three digital programs per 
 week as part of his regular course work. 
 
 After a language has been mastered to the extent of being a basic 
 tool - that is, the student has no particular difficulty (clerical errors 
 aside) in coding a problem which somebody else has analyzed, formatted and 
 flow charted, he is ready for the next stage in the learning process, namely 
 problem formulation. This is more difficult to do, more difficult to teach, 
 and is not taught often enough now. If the student succeeds in developing 
 this ability, he is ready to address himself to very difficult problems 
 over those he did not understand when he first attacked them. 
 
27 
 
 6. STRUCTURE AND CONTROL OF THE COMPUTER FACILITIES 
 
 When is computer decentralization justified? "When one division 
 of the university may use so large a fraction of the resource - perhaps as 
 little as 5$, " says Calvin C. Gotlieb, University of Toronto. We suggest 
 a more pragmatic answer to this question; namely, computer decentralization 
 is justified whenever a group has responsibility for regular operation of 
 an essential service. 
 
 It is natural for them to want control of the equipment it needs 
 for its work. Soon it becomes undesirable for this group to become completely 
 dependent on a machine which must serve as a teaching and research facility 
 for the university. Inevitably there will be occasions when the group will 
 require pre-emptive authority to have its work run first. It is well known 
 that such occasions do arise when it can be shown that there will be physical 
 hardship to the staff if work is delayed or perhaps when a machine breakdown 
 has resulted in a heavy backlog of work. Jobs for which urgency cannot be 
 demonstrated will be postponed - with the result that teaching and research 
 will often suffer. It may be that a high-priority group will have less 
 incentive to plan for an orderly expansion of facilities to meet its growing 
 needs. The result would be a progressive squeeze on those less able to find 
 funds for their share of the computer costs, or simply with less opportunity 
 to present their cases before the administrators responsible for allocating 
 time. It is just this reasoning which has led many to set up a separate 
 facility for administrative data processing. These arguments also apply to 
 
28 
 
 the rapidly approaching computer utilization in the daily operation of the 
 university library. Computer usages for circulation control, for book 
 ordering, and for maintenance of a periodical file are conventional appli- 
 cations. 
 
 6.1 Information Dissemination 
 
 Selective dissemination of information, based on matching abstracts 
 against profiles of the interests of users, and the construction of catalogs 
 on disks and tapes are in the pilot project stage. We can soon expect to 
 see indexing, catalog searching, and many other library operations carried 
 out with the aid of the computer. As libraries become increasingly depen- 
 dent for their everyday functions on computers, we can expect them - in 
 fact encourage them - to acquire their own facilities. It can be expected 
 in the hospitals with which universities are associated for teaching purposes. 
 Obvious daily uses are found in patient admission and billing, maintaining 
 drug inventories, and storage of medical records, supervision of nursing 
 stations, in-patient care, etc. 
 
 There are instances in which a computer is required to service or 
 control a single piece of equipment which acts as a major facility for a 
 large number of individuals. A particle accelerator, a bubble chamber, 
 hospital experimental operative units, can justify dedicating, which reflects 
 common parlance among computing individuals and is an indication of a complete 
 allocation of a computer resource to a particular task. 
 
 6.2 Separate and Unequal 
 
 Reiterating, a separate responsibility is likely to require a 
 separate facility. It can be recognized by the presence of a distinct 
 
29 
 
 organizational structure, with its own staff, "budget, space, and facilities, 
 and by the fact that the operation is continuous, and without any time limit 
 set for its duration. The duplication of memory and arithmetic units may 
 he offset in part by the reduction in communication costs otherwise needed 
 for transmission of data and programs to a central facility. The value 
 of advantages of decentralization can outweigh the costs of duplicating some 
 equipment. 
 
 Separate but not necessarily equal systems with a general-purpose 
 central facility larger than those dedicated to special functions is recom- 
 mended based on the belief that a central computer with large capacity memory 
 and high speed CPU, will undoubtedly be useful even to the users of the 
 "separtists." . 
 
 6-3 The Central Facility 
 
 The central facility should maintain compatibility between the 
 user groups not by name manufacturers but the machines must be able to 
 talk to one another through an established communication link, or by being 
 able to read one another's tapes or disks. It must be realized that this 
 compatibility will add to the cost of one or both of the computers - in extra 
 hardware or in extra programming; and as anyone with experience will testify, 
 it is extremely hard to maintain compatibility between two independent sys- 
 tems, even where there is a strong desire to do so. It will be impossible 
 to do this without setting up a formal mechanism of exchange, and without 
 setting up good documentation of the operational system - a plus value in 
 itself. If these communication channels among different computing groups 
 are established and maintained, the chief inefficiencies resulting from 
 multiple installations will probably be avoided. / 
 
30 
 
 G.k- Interface Compatibility 
 
 How do you enforce this interface if you allow someone, say the 
 library, to install its own computer? Furthermore, presuming that this 
 problem can be solved, so that you have the interface, you no longer have 
 separate communications, indeed, you have a network. As to the interface, 
 an advisory committee should consider, in every case whether interfaces and 
 communication channels are provided and whether they are adequate and not 
 too expensive. A computer with limited i/O equipment must include a budget 
 for such interface items as data phones. Sometimes there are alternatives 
 to data phones. An example from the University of Toronto: there physicists 
 were considering a PDP-8 for their linear accelerator. Now even though it 
 was to be a stand-alone facility, they installed a tape unit, with tapes 
 which could be read by their IBM 7^9^ • They had to buy an extra piece of 
 equipment to assure compatible tapes. This was worthwhile for not long 
 after, they were logging data which is processed on the 709^* This compati- 
 bility is not of people and programs. Compatibility is taking the form of 
 conversion, e.g., data conversions. Note how important it is to have a 
 good information distribution system. 
 
31 
 
 7- THE COMPUTER AS AN EDUCATIONAL TOOL 
 
 Now let us concern ourselves with those educational applications of the 
 computer in which the student, not a teacher or staff member is interacting with 
 the computer. Briefly, the computer can be used five ways: 
 
 1. Under the control of a previously prepared program, the computer 
 can exercise the student in skills--just as a drill master. 
 
 2. Under the control of a prepared program the computer will perform 
 the tedious calculations to expedite the student's progress through 
 various course work — a programmed desk calculator. 
 
 3- Under the control of a previously prepared program, the computer 
 will simulate in the classroom real world situations, theoretical 
 or abstract models — a simulator. 
 
 k. Under the control of a previously prepared program, the computer 
 
 will engage the student in a question-and-answer dialogue designated 
 to aid him in the formation of concepts—a tutor. 
 
 5- Not under the control of a previously prepared program, the computer 
 may serve as a sophisticated tool to be programmed by the student as 
 an aid in algorithmic thinking — a problem solver. 
 
 The computer will be a fact of the student's life in years to come. The 
 
 contact he initiates in this program will continue into his later life. The 
 
 importance of on-line use of the computer is because it teaches algorithmic 
 
 thinking. With falling costs, the computer can find its most important 
 
 application as a medium for individual instruction. The advantage of graphics 
 
 terminals for certain types of problems is very clear. It is also true, although 
 
 people who have only had experience with batch processing are unaware of this, 
 
 that program debugging is perhaps twice as fast if done from a console, even as 
 
 imperfect a one as a teletype. This is so because of powerful existing 
 
 facilities operating on user files and the ability to initiate a large number of 
 
 / 
 
32 
 
 runs in a short period of time. In this mode it gives the student prompt feed- 
 back or knowledge of his results. It adapts the content of instruction and the 
 techniques of instruction to the student's individual requirements as revealed 
 by his interaction with the computer. 
 
 7.1 The Teacher's Responsibility 
 
 A teacher's most important goal is to arm the student with all the 
 necessary tools for self -learning. An appreciation for books, a motivation to 
 study, a desire to know, an acquisition of curiosity, and yes, the computer. 
 
 In structuring a course, a teacher asks the following: 
 
 1. What specifically is to be learned? 
 
 2. How must one design achievement measures? 
 
 3. Can the course objectives be communicated to the students? 
 
 k. What acceptable proof is there that the course objectives have been 
 met? 
 
 In a question-answer series (tutorial) between student and computer, 
 wrong answers are followed by remedial explanation. Computer quiz indicates a 
 series of questions initiated by the computer and answered by the student without 
 remedial explanation. The student score is automatically recorded for the 
 teacher's records. Computer learning refers to the situation of a student 
 programming a problem for the computer in such a manner as to give greater in- 
 sight into the problem and subject matter. Computer simulation indicates a 
 program which causes the computer to mimic physical phenomena and to graphically 
 display the results. This allows the student to study the nature of a situation 
 and analyze the consequences of several actions before approaching the actual 
 physical problem. Less time is spent in the drudgery of physical experimentation 
 
33 
 
 7-2 The Student Stimulated 
 
 A lack of a mathematical aptitude or inclination often makes the 
 physics course, for example, a discouraging experience. Interesting and 
 vital concepts of physics need not be lost for one may use the computer to 
 assist students with varying mathematical abilities to understand and retain 
 both the mathematical manipulations and the concepts of physics. Most early 
 mathematicians, I note, did a tremendous amount of numerical experimentation. 
 Gauss was a supreme example of this. They found facts, relations and 
 patterns before they decided what was true and tried to prove it. Likewise, 
 many students don't really appreciate what the facts are because they learn 
 formulas but don't get to look at numbers or graphs. 
 
 Note the normally written equation forms of the man-made axioms 
 of natural phenomena found in problem-oriented courses (mathematical or 
 logic in contrast to biology, or business in contrast to history) . Use of 
 the computer in these problem-oriented courses removes the idealizing 
 assumptions: no longer is the closed-form analytical solution required. One 
 might let the computer output drive an oscilloscope so 'that the student's 
 solution becomes immediately visible. Many problems have been given the 
 student, that by necessity, assumptions are made which are known to differ 
 from the actual physical phenomenon being studied. The computer's speed 
 allows the consideration of "non- idealized" situations. While the 
 consideration of air resistance or changing force of gravity is beyond the 
 scope of most elementary physics textbooks, with the computer even the 
 non-science students can be made to realize the effects of numerous real 
 parameters on the solution of existing problems. 
 
3h 
 
 Consider courses where no computer language is required; i.e., the 
 student learns to operate the computer terminal and necessary instructional 
 information is prepared (preprogrammed by the teacher) . This method is well 
 suited for those requiring considerable amounts of drill and training — repetitive 
 exposure, and memorization. Electrical engineering students must be trained to 
 operate the oscilloscopes for signal measurement and detection. The computer is 
 used to lead the student through a series of training steps followed by questions 
 to probe the student's understanding. Progression comes after mastering previous 
 steps. While most courses require some drill and training, some courses seem to 
 require more than others, for instance: languages more than mathematics, medicin* 
 more than economics, and chemistry more than engineering. Subject matter for 
 drill and training is presented in question and answer form very similar to the 
 programmed textbook. The computer has the advantage of flexible presentation of 
 the next learning frame, and continual record keeping of the student responses. 
 The computer terminal can display pictures and graphs, or can be made to access 
 a slide-projector cartridge. The obvious advantage of the computer for drill and 
 training is that the student is self -paced and continually informed of any 
 deficiencies in retention of subject matter. 
 
 7.3 Programmed Course Work 
 
 "The only way to learn a subject is to teach a subject" is often heard 
 (and true.' )• The student needs to take a more active role in the learning procesi 
 and to set the pace in relation to his own limitations. The teacher of a course 
 would present the student with a list of objectives which he must master before 
 the teacher will be convinced that the student has fulfilled his responsibilities 
 of "knowing" the subject. The physics student may be told at the completion of a 
 
35 
 
 
 certain segment of the course, he must be able to: 
 
 1. Derive Maxwell's equations. 
 
 2. Demonstrate Conservation of Energy. 
 3- Plot distance as a function of time. 
 
 By letting the computer manage the student response data the teacher 
 can immediately see when and how often each student has used the computer; and, 
 there is a record of all correct and incorrect responses making it possible for 
 the teacher to pinpoint difficulties in student understanding and insuring prompt 
 remedial action. The student need not "guess" what the teacher requires of him 
 or what the teacher thinks is important, for realistic course objectives are 
 monitored by the computer. The student may be given the following objectives: 
 
 1. Determine the motion of a mass-spring system when acted upon by 
 a force. 
 
 2. Write a computer program to determine the position of the mass at 
 any time. 
 
 3- Prepare a computer program to plot the results of part 2, above. 
 
 A statistics course taught with the aid of a computer is exciting. No 
 longer do coins or dice have to be tossed 10,000 times; using the random number 
 generator enables samples of this size to be simulated in seconds. Using avail- 
 able algorithms students can plot the sampling distributions and can approximate 
 the statistical tables. ( Statistics - -Traditional and Bayesian , Victor E. McGee, 
 Appleton-Century-Crofts, 1968). 
 
 The computer is employed to assist the teaching of an optics lab where 
 exact calculations are tedious and uninteresting. Students also turn to the 
 computer as a matter of course in order to carry out such tasks as experimental 
 curve -fitting, solution of differential equations and other numerical 
 integrations. Monte Carlo calculations, and routine arithmetic manipulations 
 
36 
 
 formerly consigned to the desk calculator. Graduate students find it a vital 
 research tool, as do some faculty members, who also depend on it to process grade 
 in the high -enrollment courses. 
 
 What about a lab organized around the computer in a way that the 
 physical phenomena of mechanics might be displayed in tight conjunction with the 
 math models intended to describe them. The student would be permitted to "play" 
 with the parameters of the theory, much in the same way that he plays with 
 experimental parameters in a conventional laboratory. 
 
 7.4 The Team: Student-Teacher-Machine 
 
 It is not a question of man versus the computers but the tasks should 
 be done by man-machine teams. Suppose we are given a problem involving millions 
 of computations. The programmer must foresee everything that could possibly 
 happen during the logical chain, and provide for it in his program. Human beings 
 are not very good at doing this. Or, if they succeed, the price is tremendously 
 complex programs that must provide for all kinds of catastrophes, most of which 
 never occur. By letting the machine do a reasonable piece of the work and then 
 report the results to the programmer, he can then use his judgement as to whether 
 to proceed, or to change the plan of operation. It is thus not necessary to 
 program human common sense; it can be applied by the human being when needed. 
 
 The point is, learn how to work with the computer in solving a problem, 
 rather than submitting a problem for machine solution. It is the student 
 "teaching" the computer. By being able to program certain processes, the student 
 necessarily shows a thorough understanding of the process. Writing a program to 
 add fractions shows a complete understanding of the process. To develop the 
 manual skill for performing such calculations, the computer can be easily used to 
 drill the student. 
 
37 
 
 The computer has the additional advantage of encouraging the student to 
 admit that he has not learned or understood a particular concept. In contrast, 
 all teachers have experienced the natural reluctance of students to ask questions 
 in class for fear of exposing their culpable ignorance of the subject matter. The 
 computer presents a problem to the student and waits for the response. Depending 
 on the user's response, the program will give the student a hint, show him how to 
 work the problem, or give him another problem. In this way, the tutorial session 
 is tailored to meet the individual student's needs. 
 
 Rather than just listening in class, the student is encouraged to take 
 notes (pencil and paper become tools for learning). This same student reads about 
 the thoughts of others in books (learning tools) and he may use problem workbooks 
 or programmed textbooks. The student has also been taught to make use of 
 libraries and film to further his understanding of subject matter. The digital 
 computer now poses the question of combining the advantages of existing eductional 
 tools with those new tools and concepts derived from computer technology. How to 
 stimulate and guide students into this active role of acquiring the skill to 
 search and organize a field of study essentially augmenting their abilities by 
 means of a computer presents a real challenge to teachers everywhere. Repeating, 
 the student must be guided to explore concepts with the computer which were 
 impossible or impractical by normal classroom techniques. 
 
 7« 5 The 3tudent/Teacher ' s Records Keeper 
 
 With the computer designed to store and retrieve vast amounts of data, 
 it is not surprising that we consider its role as academic records keeper. If 
 one considers homework, laboratory and daily class work, plus examinations, a 
 student can easily generate fifty items of data in a semester. Fifty data points 
 times about as many students could reduce the teachers role to that of a full-time 
 
38 
 
 record keeper. The teacher may require the computer to compare the current class 
 with previous classes and in this manner have an indication of whether to spend 
 more or less time on certain subject matter. The computer would thus relieve the 
 teacher of much tedious record keeping and allow more time for direct interaction 
 with the students both as a group and as individuals. The computer becomes a 
 management and deci si on -making tool for the teacher, constantly informing him of 
 the progress and differences of each individual student. 
 
 The computer has the capability to store in its memory the complete 
 picture of a student's abilities, aptitudes and desires, and to compare these witl: 
 the professional requirements of numerous careers, thus making it an informal 
 student counselor. 
 
 The calculations made by the computer are so rapid that individual 
 points and line segments can be continuously displayed on a CRT. CRT results can 
 be filmed and shown to groups or classes of students; e.g., in a physics class 
 dealing with vectors, one might imagine describing the addition of vector 
 quantities by a computer-generated display of a continuous sum of two rotation 
 vectors. In chemistry, the symmetry of molecules can be studied by a computer 
 model relating such parameters as bond angle, bond length, and atom location. 
 For the teacher of engineering, drawings will find considerable application of 
 the three-dimensional computer display of design objects. These objects can be 
 rotated and inspected from several views on a graphic computer terminal. 
 Consider writing the script, producing and directing a computer animated 
 solution to this: the production of a square wave using Fourier terms needed for 
 the solution. This animated version of a normally complicated problem lends much 
 interest to the classroom demonstration. 
 
39 
 
 A final example may be found in the natural language conversation 
 between man and computer: the ELIZA program developed at MIT under Project MAC. 
 The computer is programmed to analyze input sentences on the basis of 
 "decomposition rules" which are triggered by key words appearing in the input 
 text. Responses are generated in reverse, that is, "reassembly rules" associated 
 with selected "decomposition rules". The choice of the key word in the input 
 statement is important. For example, in the line, "Men are all alike", 'alike' 
 is chosen as the key, and a routine response returns, "in what way". 
 
 In conclusion, a computer-integrated course exposes the student to 
 computer techniques within the framework of the normal course. An undergraduate 
 physics course would enable science students to acquire computer skills by solving 
 physics problems on the computer during the semester. Non-science students, many 
 of whom will later be in decision-making roles in industry and government, must 
 also be exposed to computing and its practice, its powers, and its limitations. 
 The type of exposure to the computer depends upon the subject matter, and the type 
 of student participation planned. The selection of a computer system and its 
 utilization falls within two broad categories, each of which is dependent upon 
 the kind and amount of student involvement: 
 
 1. The student programs on the computer an assigned problem and obtains 
 his own solutions. 
 
 2. The student changes the data parameters of an existing program and 
 learns through analysis of the computer -generated results. 
 
40 
 
 8. THE MINICOMPUTER 
 
 As noted, it is one thing to teach a student to use a computer 
 while it is an entirely different problem when considering the use of the 
 computer to teach the pupil (or even considering the pupil "teaching" the 
 computer). Yet, in any case, to attain these goals the computer facility 
 must be readily available; the physical plant and the media of student- 
 machine communication. 
 
 Having passed through the three major communication media cycles: 
 verbal — the communicator and his audience were in direct contact; literal — 
 information transmitted word/sound by word/sound; optical — a picture is 
 worth a thousand words; we are now in the "age" of electronics. We can 
 utilize all three media in reinforcement of each other and, furthermore, 
 implimented by the tactile element of muscular learning as the man and ma- 
 chine interface (interact). 
 
 Consider now an addition to the educational environment: the 
 "computer laboratory". This laboratory would be a room dedicated to a 
 computer service. It would include instructional materials as supplied by 
 the faculty, "reserved" textbooks, and possibly, high demand periodicals. 
 A consultant would be available at all times; there would be a consultant 
 for each "laboratory". 
 
 The remainder of this paper will be a discussion on how this 
 "laboratory" can provide fast turn-around performance for the minimum 
 cost. First, turn to Table #1. This table is entered as an indicator of 
 the "high" cost of computation. This table gives the number of operations 
 
kl 
 
 possible for one dollar ($1.00). It includes the medium-to-large machines 
 that give the most operations for the common cost; those missing will not 
 give you as many operations for your money. 
 
 
k2 
 
 TABLE 1 
 
 Cost/Performance Standardized to the 1970 Edition, 
 Auerbach Computer Characteristics Digest 
 
 SYSTEM 
 
 IDENTIFICATION 
 
 C0NFIGUPATI0N STANDARD 
 
 OPERATIONS /$!. 00 
 
 BURROUGHS 
 
 B5500 
 B5500 
 B6500 
 
 III 
 VIIA 
 
 VII I A 
 
 1.231k 
 .9318 
 1.5 
 
 TT59T 
 2.U806 
 5.U12 
 3.991 
 9.3U6 
 3.983 
 5.930 
 5.8U8 
 U.169 
 8.731 
 6.739 
 U.505 
 3.769 
 
 x 10 6 
 x 10E 6 
 x 10E 7 
 
 CDC 
 
 3100 
 3100 
 3300 
 
 3300 
 3^00 
 3^00 
 3600 
 3600 
 3600 
 6U00 
 61+00 
 6600 
 6600 
 
 VI 
 VIIA 
 
 VI 
 
 VIIA 
 
 VI 
 
 VIIIB 
 
 VIB 
 
 VIIB 
 
 VIIIB 
 
 VIIA 
 
 VIIIA 
 
 VIIA 
 
 VIIIA 
 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 
 10E 7 
 
 G.E, 
 
 215 
 215 
 225 
 235 
 U15 
 U25 
 H35 
 635 
 
 I 
 
 VI 
 
 VI 
 
 VI 
 VIIA 
 VIIA 
 VIIA 
 VIIA 
 
 2.0583 
 
 1.5178 
 
 1.8575 
 
 1.2155 
 
 1.5602 
 
 2.0366 
 
 .22U9 
 
 M39 
 
 1.600U 
 
 1.0855 
 
 1.3^9 
 
 1.U022 
 
 1.6729 
 
 .8612 
 
 .6637 
 .5155 
 
 .U266 
 .3870 
 1.391U 
 1.1700 
 .8353 
 .2035 
 .1653 
 .1093 
 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 
 10E 7 
 
 HONEYWELL 
 
 1200 
 1200 
 2200 
 3200 
 U200 
 8200 
 
 Uoo 
 
 Uoo 
 
 1U00 
 
 1U00 
 
 1U00 
 
 800 
 
 800 
 
 1800 
 
 1800 
 
 1800 
 
 VI 
 VIIA 
 VIIB 
 VIIB 
 VIIB 
 VIIA 
 
 II 
 III 
 
 II 
 III 
 
 VI 
 
 VI 
 VIIB 
 
 VI 
 VIIA 
 VIIIB 
 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 x 10E 
 
 10E 
 
 10E 6 
 
 1QE 7 
 
 10E 
 
 T 
 
 6 
 6 
 6 
 6 
 7 
 5 
 5 
 5 
 5 
 5 
 6 
 
 7 
 
 10E 7 
 
h3 
 
 TABLE 1 (continued) 
 
 SYSTEM 
 
 IDENTIFICATION 
 
 CONFIGURATION STANDARD 
 
 OPERATIONS /$!. 00 
 
 IBM 
 
 360/25 
 
 360/30 
 360A0 
 
 360/UU 
 360/50 
 
 360/65 
 360/75 
 
 360/85 
 360/165 
 
 7010 
 7010 
 70U0 
 70UI+ 
 707U 
 7090 
 709^-1 
 
 I 
 
 III 
 
 IVR 
 
 I 
 
 III 
 
 II 
 
 III 
 
 VI 
 
 VI I A 
 
 XI 
 III 
 VIIA 
 VIIB 
 VIIB 
 VIIB 
 VIIIB 
 VIIIB 
 
 III 
 
 VIIB 
 
 VIIA 
 
 VIIA 
 
 VIIB 
 
 VIIB 
 
 VIIB 
 
 .6965 x 
 
 .3887 x 
 
 .2563 x 
 
 .81*73 x 
 
 .1+999 x 
 
 1.U802 x 
 
 1.3018 x 
 
 .9212 X 
 
 2.8688 x 
 
 U.288 x 
 
 .3866 x 
 
 .3020 x 
 
 .2727 x 
 
 .9902 x 
 
 .977 x 
 
 .721 X 
 
 1.267 x 
 
 2-6 
 
 .62U3 x 
 .1+86U x 
 1.535*+ x 
 .1670 x 
 .6116 x 
 .1010 x 
 .2102 x 
 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 
 10E 5 
 10E 5 
 10E 6 
 10E 7 
 10E 6 
 10E 7 
 10E 7 
 
 NCR CENTURY 
 
 100 
 200 
 
 IIIC 
 IIIC 
 
 1.315 
 1.203 
 
 10E 5 
 10E 7 
 
 10E IT 
 10E 7 
 10E 6 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 10E 5 
 10E 5 
 10E 7 
 10E 7 
 
 RCA 
 
 70/35 
 70/1+5 
 
 70/55 
 
 70/60 
 
 301 
 
 3301 
 3301 
 
 I 
 III 
 VIIB 
 III 
 VIIB 
 III 
 VIIIB 
 I 
 VI 
 VI 
 VIIB 
 
 1.066 x 
 
 .151*7 x 
 .8350 X 
 .3652 X 
 
 .1U876X 
 
 .3062 X 
 
 .1399 x 
 
 .U73I+ X 
 
 3.139*+ x 
 
 .7086 x 
 
 .1+679 x 
 
 UNI VAC 
 
 III 
 
 1+90 
 
 1+91/1+92 
 
 1+91+ 
 
 1106 
 1106 
 1108 
 1108 
 
 III 
 
 VIIA 
 
 III 
 
 VIA 
 III 
 VIIA 
 VIIA 
 
 VIIIA 
 VIIA 
 
 VIIIA 
 
 1.520 x 
 
 1.293 x 
 
 .3537 x 
 
 .2015 x 
 
 .2506 x 
 
 .2052 x 
 
 1.787 x 
 
 1.099 x 
 
 1.51+5 x 
 
 l.llU X 
 
 10E 
 10E 
 10E 
 10E 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 10E 7 
 
kk 
 
 TABLE 1 (continued) 
 
 SYSTEM 
 
 IDENTIFICATION 
 
 CONFIGURATION STANDARD 
 
 OPERATIONS /$!. 00 
 
 ILLIAC IV 
 PDP 10 
 PDP 11 
 
 60 x 10E 7 Est. 
 
 3 x 10E T Est. 
 
 25 x 10E T Est. 
 
J+5 
 
 8.1 The Cost/Performance Ratio: Reduced 
 
 Enter the Minicomputer — the cheapest form of digital logic 
 system that you can buy today! Is not this the answer to the question, 
 "Why is it that many of the tasks once handled by the hardwired logic 
 system or "by the large, expensive computers are now being done by these 
 small, programmable digital computers?" 
 
 When acquiring a computer, one can expect to incur costs in these 
 areas: acquisition, space, supplies, and maintenance. Housing a computer 
 may also create problems of space, power, and air-conditioning. For- 
 tunately, such requirements are virtually non-existent among the new 
 minicomputers. Most may be housed in a well-ventilated closet, if 
 necessary. They require no special air-conditioning and run on standard 
 110-volt , 60 cycle power. 
 
 The annual cost of a maintenance contract will average one per- 
 cent of the total purchase price on purely electronic equipment, and k.5 
 to 6 percent on electromechanical units. In general, the purely elec- 
 tronic equipment, such as a central processor, is far less expensive per 
 unit of processing power (and much more reliable) than are electromechanical 
 units such as card readers, printers, and teletype-writers. 
 
 Note that a computer is most economical when (l) the work load 
 in the system is sufficient to utilize the equipment fully; and (2)it will 
 not be necessary to get rid of the equipment after a year or so. This is 
 an important point when considering the minicomputer. 
 
 The following few sets of statements might be useful, when, in 
 
KG 
 
 the decision-making procedure, a computer is to be chosen: 
 
 1. What are the applications to which the computer will be applied? 
 
 2. The applications require what from the computer system: require- 
 ments of language, input/output, storage, throughput responsiveness 
 
 3. Select the computer service which offers the utilization techniques 
 required and best meets other application requirements. 
 
 k. What type of computer utilization offers the throughput and 
 responsiveness--time-sharing, batch-processing, etc.? 
 
 5. Which vendor can provide this system at the least cost? 
 
 But, it is not all that simple. 
 
 8.2 The Minicomputer Defined 
 
 Before continuing let us get to the starting point: a very basic 
 definition of the minicomputer (certainly there is no consensus of opinion, yet 
 for this paper this will stand) ; a minicomputer is a small digital computer with 
 word lengths ranging from 8-l8 bits. They have around 1-usec-cycle time, 8K word 
 of core (memory) and a Teletype ASR 33 sell for $2,650 - $16,000.00. 
 
 A few years ago, no computers were anywhere near this expensive, and 
 the cheaper computers were very slow indeed. Cheap, fast integrated circuits, 
 highly reliable and mass-produced, allowed modest sized computers to be mass- 
 produced remarkably inexpensively. Furthermore, the speed has increased. Racks 
 of the past are now fitted on a few printed circuit boards. With most minis, 
 using a 3-wire, 3D organization with 20-mil cores in a planar array, technology 
 produces in 200 square inches a printed circuit board, kK l6-bit memory package 
 capable of responding with a 1 micro-second cycle time (and less). 
 
 Generally, decimal arithmetic, floating point arithmetic, searches, and 
 byte manipulation instructions are missing from the minicomputer, as are the 
 operations of divide and multiply. While the large machine provide multiple 
 position shifts, many of the minis provide only single position shifts. 
 
hi 
 
 Thirdly, by shortening the number of bits stored, transferred and 
 operated on, a definitive characteristic of minis, helps in the cost reduction. 
 If performance, achieved with the short data word length, can be di mi nished, 
 double precision programming might achieve the required results. The retail 
 price of a computer depends on hardware and software costs. Being a modest little 
 computer, a mini needs a good but not universal programming system- Most 
 manufacturers supply for their machines a basic, a FORTRAN, an assembler, a text 
 editor, a debugging program and a time-sharing system. The total effort required 
 to code up such a system is relatively small, and is charged against a large 
 number of machines. Furthermore, the owners of minis include some very sophisti- 
 cated computing types who are able to justify and acquire their own computers. 
 Thus, user groups can exchange very good programs. 
 
 Cheap as they are, minicomputers may not be the final answer to all 
 problems. Furthermore, we may choose among the minis a more expensive model if 
 the total system becomes sufficiently better. 
 
 8.3 Minicomputers — Contrasted and Compared 
 
 Many people are misled by the name "Minicomputer" into thinking that 
 they are not fast and not general-purpose computers. In this section, we get 
 down to the details of the computer architecture in order to see that they are 
 well organized, fast, and being of recent design, have more up-to-date features 
 not found in the bigger, older computers. Of course, one should always consider 
 a question: Does the value of the job to be done justify the cost of the system? 
 Note that, at the Spring (1970) Joint Computer Conference, it was reported that 
 sixty-two different manufacturers are presenting to the user nearly one-hundred 
 different minicomputers with a basic price less than $20,000.00. (Bell Telephone 
 Laboratories use one -hundred-twenty minis of which twelve different manufacturers 
 
kQ 
 
 have supplied thirty-four different models with varying characteristics to satisfy 
 their many specific applicational needs). 
 
 Starting with a typical minicomputer, Table 2 contains characteristics 
 on seventeen models from fifteen manufacturers. 
 
49 
 
 TABLE 2 
 Minicomputer Characteristics 
 
 MANUFACTURER 
 
 MODEL 
 
 PRICE MINIMUM 
 CONFIGURATION 
 
 TIME (microsec. ) 
 CYCLE ADD MULTIPLY 
 
 Clary Datacomp Systems, Inc. 
 4o4 Juniper Serra Drive 
 San Gabriel, CA 
 
 Datacomp 
 
 4o4 
 
 $ 8850 
 
 (4K) 
 
 2 
 
 
 98 
 
 Compiler Systems, Inc. 
 P. 0. Box 366 
 Ridgefield, CN 
 
 CSI-24 
 
 $14950 
 
 (4k) 
 
 .9 
 
 1.6 
 
 6.6 
 
 Computer Automation, Inc. 
 895 West l6th Street 
 Newport, Beach, CA 
 
 216 
 
 $ 7990 
 
 (4K) 
 
 2.66 
 
 5.3 
 
 42 
 
 Data General Corp. 
 Southboro, MA 
 
 Supernova 
 
 $ 9600 
 
 (4K) 
 
 .8 
 
 .8 
 
 3.8 
 
 Digital Equipment Corp. 
 l46 Main Street 
 Maynard, MA 
 
 PDP-11 
 
 $10800 
 
 (4k) 
 
 1.2 
 
 2.3 
 
 4.5 
 
 Digital Scientific Corp. 
 22455 Sorrento Valley Road 
 San Diego, CA 
 
 META4 
 
 $15650 
 
 (4K) 
 
 .9 
 
 1.8 
 
 5.9 
 
 Hewlett-Packard Co. 
 Cupertino Division 
 
 2115A 
 
 $1^500 
 
 (4K) 
 
 2 
 
 4 
 
 187 
 
 11000 Wolfe Road 
 Cupertino, CA 
 
 2116B 
 
 $24000 
 
 (8K) 
 
 1.6 
 
 3.2 
 
 19.2 
 
 Interdata, Inc. 
 
 Model 4 
 
 $10900 
 
 (8K) 
 
 1 
 
 3.o 
 
 22.8 
 
 2 Crescent Place 
 0ceanport ? NJ 
 
 Model 5 
 
 $15600 
 
 C8K) 
 
 1 
 
 2 
 
 22 
 
 Multidata, Inc. 
 7300 Bolsa Avenue 
 Westminister, CA 
 
 Model A 
 
 $14995 (4K) 
 with tty & 
 disk 
 
 .88 
 
 4 
 
 10 
 
 Raytheon 
 
 2700 South Fairview Street 
 
 Santa Ana, CA 
 
 704 
 
 $ 9750 
 
 (4k) 
 
 1 
 
 2 
 
 7 
 
 Tempo Computers, Inc. 
 
 1550 South State College Blvd. 
 
 Anaheim j CA 
 
 Tempo I 
 
 $13800 
 
 (4k) 
 
 .9 
 
 1.8 
 
 5.1 
 
 Texas Instruments 
 P. 0. Box 66027 
 Houston, TX 
 
 TI-980 
 
 $16700 
 
 (4K) 
 
 1 
 
 2 
 
 6.5 
 
 Unicomp, Inc. 
 
 18219 Parthemia Street 
 
 Northridge, CA 
 
 Comp-l8 
 
 $10500 
 
 (4K) 
 
 .88 
 
 1.8 
 
 8.1 
 
 Varian Data Machines, Inc. 
 2722 Michelson Drive 
 Irvine , CA 
 
 620/f 
 
 $10500 
 
 (4k) 
 
 .75 
 
 1.5 
 
 3.1 
 
 Wang Laboratories, Inc. 
 
 3300 
 
 $ 7200 
 
 (4k) 
 
 1.6 
 
 4.8 
 
 software 
 
 836 North Street 
 Tewksbury, MA 
 
 with tty 
 
50 
 
 TABLE 2 (continued) 
 
 MODEL 
 
 OPERATING SYSTEMS AND LANGUAGES 
 
 1/0 
 
 EQUIPMENT* 
 
 MAX. I/O 
 (KILBYTES/SEC) 
 
 MAX. MEM. 
 SIZE 
 
 Datacomp. 
 
 kok 
 
 COBOL, basic, timeshare exec. 
 
 tty 
 
 UJO 
 
 65K 
 
 CSI-2U 
 
 ALG0L-60, basic, FORTRAN IV, 
 timeshare exec. 
 
 disk,mtc, 
 mt ,cr,tty 
 
 3,300 
 
 8000K 
 
 216 
 
 1, 2, or 3 pass assembler, 
 basic 
 
 cr,pt,tty, 
 
 lp,mtc,crt, 
 
 disk 
 
 500 
 
 32K 
 
 Supernova 
 
 assembler, timeshare, basic 
 FORTRAN IV, ALGOL, DOS 
 
 tty,cr,pt, 
 pi, mt, disk 
 
 870 
 
 32K 
 
 PDP-11/20 
 
 assembler, basic, FORTRAN 
 
 disk,pt ,cr , 
 tty, crt, 
 mt ,pl,lp 
 
 1,660 
 
 32K 
 
 METAU 
 
 batch monitor, real-time exec, 
 1130 and 1180 emulator 
 
 cr ,pt ,mt , 
 lp,disk, 
 
 2,U00 
 
 65K 
 
 2115A basic control system, DOS, 
 FORTRAN, ALGOL, basic 
 
 3300 
 
 cr,pt,mt , 
 lp, crt , disk 
 Pl,typ, 
 marked card 
 
 500 
 
 basic, time sharing 
 
 disk,mtc, 
 tty,typ 
 
 300 
 
 8K 
 
 2116B 
 
 same as 2115A plus real-time 
 exec. 
 
 same as 
 2115A 
 
 600 
 
 32K 
 
 Model h 
 
 assembler, basic, OS, real-time 
 OS, FORTRAN IV 
 
 pt ,mt,cr , 
 
 500 
 
 65K 
 
 Model 5 
 
 same as Model h 
 
 pt ,mt ,cr, 
 drum, disk 
 
 500 
 
 32K 
 
 Model A 
 
 basic, FORTRAN, OS 
 
 cr ,disk,lp, 
 mt ,mtc,pl 
 
 2,000 
 
 65K 
 
 70U 
 
 1 and 2 pass assembler, 
 
 FORTRAN IV, SYMII , basic FORTRAN 
 
 cr, disk, pi, 
 mt ,mtc ,pl, 
 pt,tty 
 
 2,000 
 
 32K 
 
 Tempo I 
 
 Tempo I, FORTRAN IV 
 
 cr, crt , disk, 
 drum,lp,mt , 
 pt,tty 
 
 l.UOO 
 
 256K 
 
 TI-980 
 
 FORTRAN IV, DOS, real-time, 
 multiprogramming 
 
 cr ,disk, 
 lp,pt 
 
 2,000 
 
 65K 
 
 Comp-l8 
 
 1 or 2 pass assembler, basic 
 
 crt ,mt , 
 pt,tty 
 
 2,200 
 
 26 2K 
 
 620/f 
 
 basic, data assembly system, 
 FORTRAN IV, master operating 
 system 
 
 cr ,disk,lp, 
 drum,mt ,mtc, 
 pl.pt, tty 
 
 276 
 
 32K 
 
 65K 
 
 cr = 
 mtc : 
 tty ■■ 
 
 card reader; lp = line printer; mt = magnetic tape drive 
 : magnetic tape cassette; pi = plotter; pt = paper tape reader; 
 : teletypewriter; typ - typewriter 
 
51 
 
 TABLE 2 (continued) 
 
 MODEL 
 
 NUMBER OF 
 INSTRUCTIONS 
 
 WORD LENGTH 
 (BITS) 
 
 NO. PRIORITY 
 INTERRUPTS 
 
 NUMBER OF 
 DNA CHANNELS 
 
 ADDRESSING 
 TECHNIQUES 
 
 Data Comp 
 
 4o4 
 
 46 
 
 16 
 
 15-256 
 
 4 
 
 
 
 CSI-24 
 
 32 
 
 24 
 
 U-256 
 
 1-256 
 
 
 direct , 
 indirect indexed 
 
 216 
 
 122 
 
 16 
 
 3-64 
 
 0-8 
 
 
 direct, indirect 
 indexed, relative 
 
 Supernova 
 
 200 
 
 16 
 
 -16 
 
 1 multi 
 
 .plexed 
 
 direct, relative 
 
 PDP-11/20 
 
 Uoo 
 
 (handwired) 
 
 16 
 
 4 expendable 
 
 256 
 
 
 direct 
 
 METAU 
 
 27 
 
 16 
 
 6-32 
 
 9 
 
 
 direct 
 
 211 5 A 
 
 TO 
 
 16 
 
 8-4 
 
 0-2 
 
 
 indirect, 
 partial direct 
 
 2116B 
 
 TO 
 
 16 
 
 16-48 
 
 0-2 
 
 
 indirect, 
 partial direct 
 
 Model 4 
 
 92 
 
 16 
 
 1-255 
 
 T 
 
 
 direct 
 
 Model 5 
 
 123 
 
 16 
 
 1-255 
 
 T 
 
 
 direct 
 
 Model A 
 
 163 
 
 16 
 
 -384 
 
 1-8 
 
 
 indirect, indexed 
 relative 
 
 Model T04 
 
 T4 
 
 16 
 
 1-16 
 
 6 
 
 
 direct, indexed 
 
 Tempo I 
 
 9T 
 
 16 
 
 4-16 
 
 0-7 
 
 
 direct, indirect, 
 indexed, relative, 
 immediate 
 
 TI-980 
 
 85 
 
 16 
 
 3-256 
 
 1-8 
 
 direct, indexed, 
 base register, 
 indirect, relative 
 immediate 
 
 Comp-l8 
 620/f 
 
 31 
 
 18 
 
 1-64 
 
 ~~ 6T 
 
 1-16 
 ~T6~ 
 
 direct, indirect, 
 indexed 
 
 135 
 
 16 
 
 direct, multi- 
 level indirect, 
 indirect index, 
 pre-index, post- 
 index, immediate, 
 extended 
 
 3300 
 
 T2 
 
 8-128 
 
 page indexed 
 
52 
 
 8. 3*1 Minicomputer Description 
 8.3'1«1 Block Diagram 
 
 Observe, Figure 1, how a digital computer interfaces with man and the 
 real world. The keypunches, keyboards, teletypes, and telephone networks that 
 operate with digital computers are essentially digital in nature. Through print- 
 ed characters man interacts with this digital communication. The central proces- 
 sing unit, the mainframe, does all of the logical and arithmetical processing 
 associated with the computer. It utilizes a collection of (Digital) memories — 
 slow paper and magnetic tapes to very fast core memories. 
 
 Signals from a non-digital world must be converted into digital 
 parameters for use within the computer system. It may be possible that the input 
 to the digital sensors can be obtained directly. 
 
 
 
 
 
 Memori 
 
 ss 
 
 
 
 
 
 A to D 
 
 
 " 
 
 
 1 
 
 
 
 
 L 
 
 
 
 Trans- 
 ducers 
 
 
 
 
 
 
 Flow 
 
 Force 
 
 Position 
 
 Temperature 
 
 Voltage 
 
 Volume, 
 
 etc. 
 
 _ 
 
 
 4 Other Computers 
 
 
 
 i 
 
 ■ 
 
 
 ' 
 
 
 
 
 Digital 
 Sensors 
 
 
 > 
 
 ' 
 
 i 
 
 i 
 
 
 
 Digital 
 CPU 
 
 
 
 
 
 J' 
 
 
 
 
 
 
 
 
 
 1 
 
 Telephone 
 Network 
 
 
 
 
 
 
 
 
 Digital 
 Drivers 
 
 4 
 
 
 
 
 
 
 
 
 
 Trans- 
 ducers 
 
 
 
 
 
 
 
 
 
 , i 
 
 
 
 ' 
 
 
 
 
 Keyboard, Printer, 
 CRT. Plotter. P+.r*. 
 
 
 Man 
 
 
 D to A 
 
 
 
 
 t 
 
 
 
 
 
 
 
 
 
 
 
 - ? 
 
 
 
 ______ 
 
 
 Figure 1. A Digital Computer Interfaces with Man and the World 
 
53 
 
 The computer control unit of Figure 2 coordinates all the other parts of the 
 computer to insure the logical sequencing of operations "will be carried out 
 correctly and exactly at the right time. The CCU is the slave of memory (the 
 programmer's program) via the memory control unit. These instructions are 
 interpreted to produce the specific logical sequence required by each program. 
 
 8.3«1«2 Memory 
 
 The memory modules generally use magnetic storage --thousands of ferro- 
 magnetic cores. For each core, 1-bit or binary digit may be obtained. A word 
 is a collection of these bits: word lengths are 8, 12, l6, 18 bits. Bytes, 
 ordered subset of bits of a given word, may be addressable; a l6-bit word is 
 normally composed of two 8-bit bytes. Further, organization of 4,096 words 
 (4,096 times the word length equals the number of bits) is one memory module; 
 this is referred to as a kK module. Memory cycle times vary from . 5 to 5 micro- 
 seconds. 
 
 Normally one or two memory modules are purchased with the larger minis 
 handling up to 6k modules. A normal maximum is 16-4K word modules. There are 
 also IK and 2K modules. Because of the large numbers of operational registers 
 and the fact that the program of the microprogrammed MICRO Systems MICRO 800 is 
 in a read-only control memory, little if any core memory is required. Micro- 
 programming advantages will follow. The read-only memory may be included as a 
 part of the main memory or as a substitute for or in addition to the computer's 
 read-write memory. Expansion is made easy by plugging a memory module into a pre- 
 wired-to-the memory bus board position. 
 
5^ 
 
 Memory- 
 Module 
 
 A 
 D 
 D 
 I 
 T 
 I 
 
 N 
 A 
 L 
 
 M 
 E 
 M 
 
 R 
 Y 
 
 Memory- 
 Module 
 
 Arithmetic and 
 Logic Unit 
 
 Memory 
 Control 
 
 Unit 
 
 Computer 
 Control 
 Unit 
 
 Direct 
 
 Memory 
 
 Access 
 
 Unit 
 
 High-Speed 
 I/O Bus 
 
 I/O Unit 
 
 I/O Bus 
 
 > 
 
 Figure 2. Basic Minicomputer 
 
55 
 
 Under the direction of the CCU, the memory control unit, the 
 master index for insertion and retrieval of information from the new 
 modules, routes memory words to and from all the other units. The memory 
 cycle time noted above is the time it takes the memory word to go through 
 the memory control unit. Obviously, the MCU can function independently of 
 the CCU when (a) several minis share a common memory and (b) when high speed 
 data transfers pass through the direct memory access unit (DMAU). More 
 than 1 DMA controllers may be connected to the same bus. When there are 
 conflicts between the CPU and DMA a priority logic system rules in favor 
 of the DMA. Since normally there exists a single memory bus, the CPU per- 
 forms memory timing with the timing of instruction execution based on the 
 memory cycle time. Generally there does not exist an overlap of memory 
 operations . 
 
 8.3-1-3 Word and Instruction Length 
 
 One comment on the 6 to l8-bit word lengths . As the lengths 
 get shorter, the addressing process gets more complicated — more storage 
 cycles are needed per instruction cycle. The price does go down, too, 
 but so does the number of bits available for data addressing/instruction 
 codes. The 8-bit byte addressibility is certainly of high value if 
 computation is kept to a minimum and data is byte oriented (data commun- 
 ication applications). This is because the unit of addressibility corres- 
 ponds to the data unit and the processor commands are oriented toward 
 the manipulation of characters. This addressing by instruction may 
 reference the left or right bytes of the word or by treating memory as a 
 
56 
 
 class of "bytes (not words) each with an address. 
 
 While most minis are single address, binary, using the 2's 
 complement to denote negative numbers and most use single-word instruction, 
 Others do use two or three word instructions. The 8-bit machines using 
 one or three words per instruction may be considered more flexible than 
 the one-word l6-bit machine instruction. The mini, versatile as it is, 
 has limited storage capacity and computation cycles , thus efficient use 
 of each is required. 
 
 8.3.1.1^ Addressing 
 
 It should be obvious that the word does not have enough bits 
 available to the addressing section to locate each unit of the storage 
 module. With a typical 8-bit addressing operand only 256 storage locations 
 can be pointed to even with the maximum possible 9 bits , only 512 
 locations can be determined so that data might be transferred to or from 
 the memory. Where a longer memory address of say 16 bits is required, 
 it is calculated utilizing the contents of a register. 
 
 By using a double word instruction where the right word of the 
 two is used as the direct address, for a machine of word lengths of 16 
 bits, 6kY. storage cells may be directly referenced. It should be pointed 
 out that two memory cycles are required to fetch the instruction and then 
 to compute the address of the operand. By using additional computer 
 resources the range of memory location covered is extended to the entire 
 space. The indirect addressing system consists of reading a memory 
 location which is directly addressable. It uses the data word to 
 
57 
 
 represent the address of data (it is a pointer) instead of actual data; 
 the retrieved contents from the storage location from which it was 
 directed, is treated as the address of an operand to which it points. 
 
 This process can be continued into more levels of indirect 
 addressing. Where this data word represents an address of data a 
 special hit must be utilized to indicate an address, otherwise the data word 
 will be the assumed data (operand). Obviously, each time there is a 
 level change, additional memory is required because data word (address) 
 must be processed; i.e., and additional microsecond is added to the 
 instruction execution time for every level of indirect addressing (based 
 on a one microsecond storage cycle of a processor: the usual one micro- 
 second to retrieve the instruction plus the one microsecond to extract 
 the address). 
 
 Indexing, either direct or indirect, requires adding the 
 contents of the index register, another central processor register, 
 to the direct or indirect address. In DEC's PDP-11 there is automatic 
 increase/decrease of the index registers' content. When operating with 
 sequential locations this feature proves to be very efficient. Since 
 an additional storage cycle is required if the index register is located 
 in core storage, such minis run slower. 
 
 8.3.I.5 Paging 
 
 By using only the address bits in the instruction word one may 
 divide memory into fixed areas (pages) whose size is determined by the 
 lengths of the instructions address part, 2 n , n is the number of bits in 
 
58 
 
 the address portion. Normally this is a 256 (or 512) word address. 
 Only two pages can be addressed: the portion of storage numbered (0) 
 zero through 256 and the page in which the current command is located — 
 the current page. The computer logic must sense a hit in the command to 
 ascertain whether the instruction refers to direct address or current 
 page. There is no increase in the time of execution. Only one storage 
 cycle is required to obtain the instruction and compute the operand 
 address. Another technique is a scheme which is represented by floating 
 page composed of the 128 or 256 locations on either side of the current 
 instruction. For an 8-bit address length, a relative address could be 
 -128 to to 127 locations from the (current) command location; i.e., 
 given the command location 828, one might make reference to any location 
 within the range TOO — 955. This is nice for the programmer; he need not 
 concern himself with how his program is positioned/stored within the page 
 boundaries ; his only concern is that the memory reference falls within the 
 range established by the floating page centered on the current instruction. 
 One may have to reorganize the code when adding instructions between the 
 operand and the instructions. But with this scheme a page can be swapped out 
 from one location, swapped into another later, and the calculation resumed. 
 
 Registers may be addressable (explicit) or buried within 
 (implicit) the system. The first is under the control of the program, 
 while the latter are possibly dependent on other system components upon which 
 the programmer has placed demands . 
 
 8.3-2 Minicomputer Organization 
 
 In this section we will discuss the organization of a typical 
 
 minicomputer. Reference the following paragraphs to Figure J>. 
 
59 
 
 Storage 
 Buffer 
 Register 
 
 A 
 Register 
 
 Aux 
 Register 
 
 Arith. 
 Unit 
 
 Inst- 
 ruction 
 Register 
 
 Index 
 Register 
 
 Program 
 Counter 
 
 Storage 
 
 Address 
 
 Register 
 
 Memory 
 
 Figure 3- The Organization of a Typical Minicomputer 
 
6o 
 
 8.3*2.1 Registers Identified 
 
 8. 3.2. 1.1 Storage Address and Storage Buffer Registers 
 
 A pair of registers are necessary. The first is an n-bit wide storage 
 address register. It contains an n-bit pointer to a location in memory to be 
 used as a source or destination. The 2nd of the pair, the storage buffer 
 register, contains the word that will be transferred. Delivery from this bus 
 may be made also to the i/o devices, arithmetic unit, and the programmable 
 registers. 
 
 8. 3*2. 1.2 Arithmetic Register 
 
 The arithmetic (A) register is the main operational register. The 
 contents of this register will be transformed by various logical as well as 
 arithmetic operations. The result is returned to the register. 
 
 8.3*2. 1.3 Carry Register 
 
 The carry (c) register, a one-bit register, will hold a bit when carry 
 is required. This bit is used when double precision arithmetic operations are 
 required; i.e., precision extends beyond register A's capacity or the operand 
 length. This bit is also the arithmetic overflow detector register. 
 
 8.3*2. l.k Auxiliary Register 
 
 The auxiliary, (Aux), register contains the least significant half of a 
 double -precision word and of the product of a multiply instruction. In 
 conjunction with the A register, it is used for temporary storage and for data 
 shifting. 
 
 8.3*2.2 Methods of i/p Transfer 
 
 The three methods of i/O transfer are: 
 
61 
 
 1. Multiplexor i/O channel 
 
 2. Programmed data transfer 
 
 3. Direct memory access 
 
 8.3«2.2.1 Programmed Data Transfer 
 
 Although the programmed data transfer channel is the slowest, 30,000- 
 lj-0, 000 words/sec, it is the most flexible method of transfer (parallel transfer 
 of word or byte) between an i/O bus or one or more of the CPU registers. An 
 interrupt system is required. This method of controlling peripheral devices and 
 checking their status is required whenever the computer must act on input data as 
 it is being received. However, due to the probability of missed data, this is 
 not even recommended for card readers without full card buffering. 
 
 8. 3*2.2. 2 Direct Memory Access 
 
 The optional direct memory access feature (DMA) is available for 
 $2,000-$5. 000 with rates of l/2 to one million words per second. This allows 
 one or two devices to make block transfers by placing the address of the desired 
 storage hole in the DMA storage address register. With an input to the central 
 processor, there is a signal from the i/O device to indicate a data break. The 
 central processor stops the computation at the end of the current storage cycle. 
 The DMA. register are connected to the storage unit and the DMA gets to read or 
 write one cycle. Note then that one storage cycle per word transferred is lost 
 which implies a maximum transfer rate equal to the transfer rate of the storage 
 unit if all cycles are taken. 
 
 Finally, note that the devices using this DMA channel are usually 
 controlled through the commands travelling over the i/o bus which also connects 
 the devices. The chaining of block transfers as found on larger computers is 
 not found in minicomputers. 
 
62 
 
 8.3-2.2.3 Multiplexor i/O Channel 
 
 The i/O channel (multiplexor) is similar to DMA. however l6 or more 
 devices can be active simultaneously. Transfer rates vary within 100-300 
 thousand words per second. This is not all that good for it is required to have 
 up to three accesses to memory for each word transferred. (One of the memory 
 cycles is to decrement the word count and check for zero; a second memory cycle 
 is to obtain the memory address and increment it and the third memory cycle is to 
 transfer the data). The card reader, punches, line printers, slow magnetic tape 
 make effective use of this. 
 
 8.3-2.3 Interrupt Systems 
 
 i/O operations for some devices may be handled via the interrupt system, 
 but it can do other things as well. The hardware is sensitive to the occurrence 
 of certain "interrupt conditions" or "events" which require that the present 
 calculation be deferred and the processor decide which event took place, and go 
 to an appropriate routine, do something about the event, and then resume the 
 deferred calculation. When the presence of an interrupt condition is recognized, 
 the hardware must do the following: 
 
 1. store program counter 
 
 2. decide, by means of hardware or software, which interrupt condition 
 of highest priority is present 
 
 3- disable interrupts of lower priority 
 
 h. process the interrupt 
 
 5. restore program counter and then enable interrupts of lower 
 priority 
 
63 
 
 8. 3*2. 3*1 Single-Level Interrupts 
 
 Whenever a single-level interrupt occurs, the control unit looks to a 
 unique storage location to get the address of the interrupt service routine. No 
 other devices can be serviced, no interrupts will be replied to until the program 
 processes the first. Obviously, many instructions must be used to differentiate 
 between the devices, -which are on-line, that transmitted the interrupt. 
 
 8.3«2-3«2 Multiple Level Interrupt System 
 
 Up to 256 levels of hardware interrupt priorities are available in some 
 minicomputers. Each interrupting peripheral device has a priority number. On 
 some machines this may be set, device by device under program controls. There is 
 also a register in the CPU called the priority level register. When any I/O 
 device gives an interrupt request this is only granted if its priority level 
 is higher than that held in the priority register. Having interrupted, the 
 priority is raised to agree with that of the device being serviced. Likewise, on 
 return from interrupt, the priority level is lowered to that of the routine which 
 was last interrupted. 
 
 Q.k The Minicomputer's Peripherals 
 8.^.1 General 
 
 The low cost of the mini -main frame is one thing, the cost of inter- 
 facing the mini to other hardware and the cost of peripherals is yet another very 
 demanding requirement in minimizing the cost of the operating system. With the 
 shift from the large to the smaller user, or if you will, from the $1, OOO/month 
 down to the $100/month user has come a redistribution of cost. Percentage of 
 70^-30% central processor to peripherals have now been reversed to 30%- r JO<f . This 
 
6k 
 
 is due not only to the decreased costs of core memories but the desire to use 
 high cost peripheral devices on the small system to make it available to more 
 people. Also, hardware costs are closely related to labor costs which have in- 
 creased greatly. Note too, that due to automation, electronics costs have gone 
 down. Whenever required, programming function are not done by hardware. The 
 programmer gets to show his prowess in preparing the software. A software 
 package for i/o has been prepared for the user and supplied as a subroutine. 
 Note that controllers for the perpheral devices consists of a single printed 
 circuit board. No longer is it across the room or in the next cabinet but often 
 this circuit board is within the same chassis as the CPU and its memory. The 
 DEC PDP-11 treats registers in the peripheral controller as addressable memory. 
 They cause these controllers to interface directly with the computer's memory bus. 
 This provision is for peripheral device-memory transfers for direct memory I/O 
 transfers as well as CPU-memory and CPU-peripheral device transfers. 
 
 Until the latest generation of peripherals, the device controller 
 designers have had a great variety of interface circuits with which to 
 communicate. Now with the heavy use of integrated circuits a DTL or TTL gate is 
 becoming the standard peripheral interface with the minicomputer. Using 
 integrated circuit line drivers and receivers (at a higher cost) gives performance 
 superior to the balanced twisted-pair transmission lines. Using these low 
 impedence differential drivers and differential amplifier receivers with common 
 mode rejection, in conjunction with twisted-pair transmission lines, cable lengths 
 in excess of one hundred feet are possible. 
 
65 
 
 9. PERIPHERALS 
 
 What the world needs is faster teletypes.' Their present low cost 
 does supply the minis i/O requirement. It serves as a slow output printer 
 (ik minutes to dump UK words of memory) and as a cheap form of storage for 
 output from the computer. This unit serves as a keyboard for program 
 input although at a rate of 10 characters per second. Note Figure k for a 
 quick ready reference comparison for data i/O. Historically, teletypes 
 have been used for the preparation of punched paper tape which is read by 
 the computer at a later time. Now the trend is to connect all teletypes to 
 minicomputers, and do on-line creation, editing and execution of user files. 
 
 9.1 General Comparisons 
 
 While three times more expensive than TTY, an optical tape reader 
 and a high speed paper tape punch will read 30-Uo times faster and punch 
 10 times more; again, the paper tape may be prepared off-line on the TTY 
 and then read into the computer by the higher speed reader. On very modest 
 systems paper tape is used for temporary storage, for example for a multi- 
 pass assembler. Paper tape while easily damaged when rewinding is very 
 reliable even when damaged. Often it can be repaired and the data 
 recovered. 
 
 Before continuing to review the established peripheral devices, 
 let us turn to punched cards which are relatively costly but much easier to 
 edit and update. Even with the advantages and an obvious future, with 
 changes like IBM's 18 x 32 hole (matrix) card, the card with the greatest 
 
66 
 
 Fixed Head Disk 
 Punched Cards 
 Disk IBM 2310 Type 
 
 -H-H-H-l-l- 
 
 Mag Tape Cassette 
 
 Paper Tape 
 
 ASR-33 
 
 IBM 231^ Type Disk 
 
 9-Ch Mag Tape 
 
 $100.00 
 
 $10.00 ' ^\ \ 
 
 $1.00 
 
 $0.10 
 
 $0.01 
 
 Total System 
 Cost/1,000 Bytes 
 (Peripheral + 
 Interface + 
 Storage Medium) 
 
 Total Off -Line Storage-Bytes 
 
 Figure k. Total Cost/1000 Bytes of Off -Line Data Storage vs. Amount of Off -Line 
 Storage for Minicomputer i/o 
 
67 
 
 future surely must be mark sense. There are mark sense card readers which 
 will read not only punched cards but also those prepared with visual 
 markings from a pencil or pen. It would be nice to get off the teletype 
 or keypunch or even the faster, more reliable typewriter. This will be 
 reconsidered later. 
 
 The 9-ch an nel magnetic tape units, IBM format, 800 bpi, allows 
 interchange of data between the minicomputer and the EDP systems. Higher 
 expense brings about freedom of generating the tape off-line and 1600 bpi 
 recordings. 
 
 A "system 3" type, removable million byte disk cartridge, with a 
 non-removable million byte disk has an average access time of about one 
 hundred milliseconds. The minicomputer is no longer i/o bound but limited 
 by the software to maximize the mini-disk combination. Again, off-line 
 input hardware is too high except in timesharing. A typical disk storage 
 
 unit consists of 32K words capacity, 18 milliseconds access time, transfer 
 
 5 
 rate of 10 words per second, but not removable. Therefore for different 
 
 or larger amounts of data, more units are required. 
 
 Although convenient, the magnetic tape cassettes are not inter- 
 changeable, in large part, due to the lack of standardization. To reduce 
 data loss, redundant recordings are often made. This is due to a 
 reliability deficiency. 
 
 With faster and more complicated, yet smaller and cheaper, 
 computers available, the mill-stone about the man/computer system is the 
 information interface between the human user and the machine. We want to 
 transfer information into and out of the machine with as little effort 
 
68 
 
 (physical and mental) as possible. Teletypewriters are woefully in- 
 adequate due not only to their slow speed but also their rigid format. 
 Alphanumeric output at 10-15 characters per second is well below human 
 scanning speed, and input and output of graphic data is cumbersome. A 
 better console, a display device capable of handling characters, points, 
 and lines in a free format is needed. A stand-alone unit connected to a 
 standard telephone line as TTY's do should make use of the full available 
 data rate that phone lines offer. 
 
 Interactive graphics is the "ultimate" in information exchange 
 procedures between machine and man. It is unsurpassed in the rate and 
 quantity of easily digestible information it can pass to the human. When 
 the computer can communicate in pictures, lists of numbers become graphs, 
 structures can be illustrated, etc. Note the obvious use of graphics in 
 computer applications where the real world is modeled — process control, 
 simulators, etc. 
 
 9.2 0(c/M)R or Sensing 
 
 Optical Mark Reading (OMR) operates on the basis of reading marks 
 that have been entered on a form in a prescribed location (and usually a 
 short straight line). The OMR scanner seeks out such marks and reads them 
 based upon their location on the page. This differs from optical character 
 recognition (OCR) whose scanner reads based upon the shape of the 
 character. It differs from Mark Sense which is a system which reads the 
 form, similar possibly to OMR in that the form was "marked", but with an 
 electrographic pencil. The user places marks, at his option, at some 
 of various fixed places on the card, and the mark sense reader detects the 
 
69 
 
 presence of such marks by passing an electric current from one end of the 
 
 mark to the other. 
 
 Mark sensing: marks sensed electrically 
 Mark reader : marks read optically 
 
 Forms are of two basic formats: single copy forms; continuous or 
 cut or as 51 or 80 column tabulating cards. Forms will range in size 
 from 3 1/2" x k" to 8 l/2" x 11". Card forms vary from k l/V x 7 3/8" 
 for the 51 column cards to 7" x 3 l/V' for 80 column cards. 
 
 "inks" used depend on the response system used; response systems 
 may be visible, infra-red, or ultra-violet. 
 
 An item that must be closely checked is the extremely tight 
 tolerances which some readers must maintain with respect to the distance 
 between the timing marks and the mark read field. The IBM 1230 allows a 
 tolerance of only + 0.005". Similar tolerances may exist with respect to 
 skew. 
 
 Cue to the extremely high cost, my only comment on OCR is that 
 a $3000 per month OCR reader attains a breakeven point when reading 17,000 
 bills per day. Thus if sufficient amounts of input data are processed, 
 OCR probably is not only faster but also cheaper than the keypunch. A 
 30-unit keypunch installation including labor is $lU,950 per month. For 
 page reader, fourteen typewriters and typists and five proofreaders cost 
 $10,775 per month. This reader "reads" a regular typewritten sheet at a 
 rate of about four lines a second (110 characters per line). Or, if you 
 will, it would read 180 pages each minute. 
 
 9.3 Graphic Processing 
 
 The importance of graphic processing is divided between the 
 
TO 
 
 importance of vision in transmitting data to the brain (a picture is worth 
 a thousand words) and the increased high speed of computer devices. A 
 video display makes sense out of pages of character printing which the 
 programmer would have to interpret. Now interpretation can be made in a 
 moment and alterations promptly made. Graphic data simply stated is an 
 "efficient" (from the user's point of view—not the computer's) input/ 
 output technique in which information is exchanged between the user and 
 the computer in the form of "pictures". Note here that a desirable adjunct 
 to graphic output is graphic input. The "pen", an electronic pointer with 
 which data may be entered directly onto the CRT screen, is certainly advan- 
 tageous. True symbiosis of man and machine has each doing what each is 
 good at: man provides the random creativity while the computer does the 
 routine, programmable tasks and stores a complete record of transactions 
 in retrievable form. A system's use is in direct proportion to the degree 
 of cognizant interaction it provides the user; i.e., two basic requirements 
 are memory and speed. Compared to the 10-15 characters per second by a 
 teletype the 120-300 characters per second for a CRT is a welcome relief. 
 Costs for CRT's however run to $50,000 and they tie up more than one line 
 to the computer in some cases. Another apparent disadvantage is that 
 there is no hard copy. A further comment: although it is important that 
 a hard copy be available, with suitable software aids, it is not required 
 at the local console for most applications. At Project MAC, over ^QPfo of 
 the TTY output paper went directly into the trash basket. The required 
 copy is generally for record purposes (grading, etc.)--a need which can 
 be filled by a central hard-copy generator. 
 
71 
 
 There are three categories of implementation. Random scan 
 techniques are most common in both alphanumeric and line-drawing 
 applications. (Depending on the line generation technique, draw times are 
 from tens to hundreds of microseconds.) 
 
 Considering the cost trade-off, the relatively slow storage 
 tube, lacking the interactive continuity because there is no way to update 
 only a portion of the screen, has a response time of milli- seconds. It 
 may take many seconds to update a full screen. 
 
 Video scan displays are normally alphanumeric applications. 
 For applications requiring generation and frequent update of alphanumerics, 
 the video scan display is an inexpensive and reliable tool. These displays, 
 i/O terminals, are flexible, fast, and easy to modify and format data. 
 Features which would be desired are: nondestructive cursor; character and 
 line insertion and deletion; and display generation under computer control. 
 The alphanumeric CRT is more restrictive than the graphic in that it does 
 not allow underlining or leaving blanks for answers in the problem format. 
 (An underline is considered a character. Having fixed character positions 
 prohibits the display of two characters in the same position 
 simultaneously. ) 
 
 CRT displays with graphic capabilities appear best suited to 
 instructional applications. The direct random positioning of characters 
 permits superscripts and subscripts, underlining, and presentation of such 
 things as long division or complex fractions. 
 
 Some of the features considered desirable for this type of 
 device are: a touch-sensitive projector screen such that when the student 
 
72 
 
 identifies, by touch, specific parts of a display, because the device is 
 under computer control, the correctness of the response can be determined; 
 (repeat) dual processor configuration (i.e., with computer control); real- 
 time clock and pushlist subroutining permitting time-shared and re-entrant 
 code; hardware multiply and divide; at least one index register; a minimum 
 of 8K core and l6-bit word length; 10 x 10" minimum display size; long 
 persistence phosphor. And, if you will, borrowing from the Plato III, 
 superimpose "a large number" of slides on the screen. (Plasma Display 
 Panels will help provide these features when available on the market. ) 
 
73 
 
 10. REMARKS 
 
 10.1 Assumptions , Delivery, and Credibility 
 
 Minicomputers are taking over many of the tasks that have been 
 done by hardwired logic systems or by the large computers. So that one 
 might choose a minicomputer depends on how the minicomputer will be used. 
 What tasks are to be performed? Its use will determine the choice. A 
 priority list can be constructed and each manufacturer can be rated 
 according to how their computer matches these priorities. There is never 
 to be the assumption that a feature exists unless specifically listed; 
 these would be such items as cables, power supplies, or cabinets, etc. 
 Minis are marketed, by others than the manufacturer. This may affect 
 purchase for the manufacturer may not have developed additional peripheral 
 interfaces which add a certain flexibility: XDS-CF-16 is a CA-216. Check 
 the manufacturer's credentials by contacting previous customers. They 
 can provide an index of delivery, credibility and reliability. 
 
 By categorizing minicomputer applications, it is hoped that 
 important features will be exposed. The first is the stand-alone computing, 
 laboratory, and monitoring applications. It should be quite obvious that 
 in university and research laboratories stand-alone computing applications 
 typically occur. Laboratory and monitoring applications represent an 
 extension of stand-alone computing applications where usually a variety 
 of transducers, sensor, multiplexors, and analog-to-digital converters are 
 connected to the basic stand-alone system. Generalizing, this mini- 
 system is composed of direct i/O. devices, usually teletypes, but 
 
7^ 
 
 paper-tape readers and punches or card readers and line printers might be 
 added. The file storage facility includes cassettes tape along with the 
 magnetic tape, disk, or drum storage devices. In a laboratory/ 
 monitoring situation there are many tailormade monitoring i/O devices; 
 such as digital voltmeters, counters, multiplexors, oscilloscope displays, 
 plotters, special-purpose transducers and sensors, etc. 
 
 In choosing a minicomputer mainframe, begin by determining the 
 types of i/O equipment desired. Select the applicable language(s). 
 
 An integrated circuit design application might not only 
 require a strong arithmetic unit and also a paper tape reader/punch, 
 but also a CRT display with pen light. Estimate production, problem- 
 solving and software development times. The relative amount of time 
 to be spent in short problems or frequently run production programs 
 affect the choice. What commands are available may limit the system's 
 computational capabilities. An efficient arithmetic unit with short 
 add and multiply times, floating point multiply and divide, and double- 
 precision operations are desired. Mathematical and utility programs 
 such as diagnostics, text editors, and debug programs aid in automated 
 problem solving. The Varian Data Machines 620/i is used by the U.S. 
 Government in many departments. The multiprocessing computer system, 
 the MOD COMP Hi/70 by Modular Computer Systems is used in development 
 and testing laboratories for engines (reciprocating). Parameters 
 include torque, speed, fuel consumption, temperatures, pressures, etc.. 
 The Data General Super-nova has made the business market in the 
 educational system. 
 
75 
 
 Let us look in on how a Hewlett-Packard general-purpose 
 2116b minicomputer with l6 K memory is used to monitor experiments, 
 cardiac dimensions,, pressures, in conscious dogs and then derive 
 dynamic ventricular performance data. With a variety of implanted 
 sensors, the investigators measure, monitor, and record the primary 
 cardiac variables of physical dimensions, pressures, flow rate, ECG, 
 and heart rate of conscious dogs, acquiring the data under computer 
 control. After a selection is made of the segment of data that is 
 of particular interest, the data are used as source information 
 for rapid calculation by the computer of the parameters descriptive 
 of dynamic cardiac performance such as cardiac output, flow, wall 
 stresses, etc. 
 
 The minicomputer permits the on-line computation, printout, 
 and display of the measured and derived quantities. It also permits 
 the simultaneous measurement, in the intact animal, of the variables 
 for a moment-to-moment assessment of ventricular performance. 
 
 Many manufacturers are making their products for use as 
 components in larger, more complex systems. In particular, minicomputers 
 can be used as component testers, numerical control machines, transfer 
 machines, etc. Py controling i/O devices which service large computers, 
 they reduce the processor cost by performing simple data manipulation 
 tasks, control sequences and assembly procedures. 
 
 Minimum and maximum data rates for both host and peripherals 
 should be specified in addition to normal transfer rates. Buffering 
 may be needed to smooth deviations in data transfer rates. If the 
 data is to be both input and output, then the minimum i/O rate must be 
 
76 
 
 twice the peak transfer rate. The minicomputer must have a short 
 cycle time so that it can respond to all peripheral/host computer 
 within the specified time. Consider carefully the priority interrupt 
 structure and the minimum time expended in processing the interrupt. 
 Scratch pad memory, general purpose registers and multiported memory 
 minimize data loss and the failure to respond to its host under 
 interrupt conflicts. These features promote flexibility. Investigate 
 the communications code and control signals of the devices before 
 choosing the mini as a device controller. One indication of interface 
 flexibility of a particular model is off-the-shelf availability of the 
 needed interfaces. While "moving" commands are very important, 
 mathematical abilities are slight: error detection or other 
 statistical analysis may be desired. 
 
 Let us now consider the minicomputer as a data concentrating 
 system where a number of low-speed input devices such as TTY and 
 other human i/O terminals are connected. The mini then concentrates 
 all of this data to transmit it efficiently to some other device, 
 usually a larger computer. Consider also the use of the minicomputer 
 to facilitate intercomputer data transmission. 
 
 We will consider the addition of a card reader, line printer, 
 and a communication interface to a minicomputer to build a remote batch 
 terminal for a large central processor. Mass storage devices are not 
 always included but one or more indirect i/O devices in addition to the 
 communications hardware are. There may be an interface to a host 
 computer. There may be data set controllers to service various 
 common carrier data sets. 
 

 
 77 
 
 Consider momentarily a series of free-standing minicomputer 
 systems, each of which may be used as a terminal for a larger computer. 
 One might want to tailor each to some specific situation (and each 
 so designed for use "by less sophisticated personnel). Since the mini 
 is used on site, there is no need for more expensive data communication 
 facilities. The mini can, as the on-site computation is completed, 
 act as terminals, condensing the data and forward relevant parts 
 over telephone lines to the central computer facility for further 
 data processing and management information. By taking advantage 
 of a party line telephone cost and by the reduced number 
 of telephone lines, communications costs are cut. A system built 
 around Data General Corporations Nova cut the telephone bill of 
 one firm from a potential $10,000 per month to $1200 per month. 
 
 10.2 Reflections from Logicon 2+2 
 
 Consider the dependence of four linked minicomputers each 
 operating independently and efficiently on its specialized task. 
 The Logicon Inc. 's 2 Plus 2 lays claim not only to increased 
 throughput, reduced turnaround time and lower cost performance, 
 but also the elimination for line termination, multiplexer equip- 
 ment, or "front end" processors. Operator interferance is reduced 
 and so is the number of human errors. 
 
 The hardware system is based on four subsystems: 
 
 1. An i/O and control subsystem for system control; 
 this mini performs all system scheduling and i/O 
 management tasks. It controls the information 
 flow to the other subsystems. 
 
 2. Swapping is under the control of the extended 
 memory subsystem mini. 
 
78 
 
 3. The computational subsystem is for process 
 execution (user) even those functions not 
 economically done by the control processor of 
 the control subsystem. 
 
 k. For peripheral device handling, the communications 
 and mass storage subsystem, controls disk and tape 
 storage units and multiple communications lines. 
 
 Seven major components comprise the Logicon 2+2: the computational, 
 
 i/O and control, communications and mass storage, and extended 
 
 memory hardware sybsystems; and the programming, operating, and 
 
 application software systems. The logical organization of the Logicon 
 
 2 + 2 is illustrated in Figure 5. 
 
79 
 
 Computational 
 Subsystem 
 
 Process 
 Execution 
 
 i/O and Control 
 Subsystem 
 
 Communications 
 
 and 
 
 Mass Storage 
 
 System Control Device Handling 
 
 Extended Memory 
 Subsystem 
 
 Swapping 
 
 PROGRAMMING SYSTEM 
 
 Subsystem Executives 
 
 Command Processors 
 
 Language Processors 
 
 Language 
 
 Subsystems 
 Include : 
 
 - BASIC 
 
 - FORTRAN 
 
 - ASSEMBLER 
 
 APPLICATION SYSTEM 
 
 System Application 
 
 Library 
 User Application 
 
 Library 
 
 OPERATING SYSTEM 
 
 Resident Monitor 
 
 - File Manager 
 
 - I/O Manager 
 
 - Process Manager 
 
 - Data Base Manager 
 
 - Utility Manager 
 
 Executive 
 File System 
 
 T 
 
 User 
 1 
 
 User 
 n 
 
 Figure 5« Logicon 2+2 System Logical Structure 
 
80 
 
 11. WHERE FROM HERE 
 
 11. 1 Microprogramming 
 
 Microprogramming should play a major role in future 
 minicomputers. While it will he assumed that the concepts of 
 microprogramming are known, the objective of this chapter will be to 
 discuss advantages of microprogramming. A microprogrammed computer 
 employes a stored program repertoire for the control unit rather 
 than fixed wiring--the control unit is not fixed but instead it is 
 programmable . 
 
 The control sequencing is implemented by a control storage 
 element and a counter to address the current microprogram location. 
 The control storage contains the microcommands which are decoded and 
 executed. The microcommands perform elementary operations, they are 
 executed in one clock step, so that a time sequence of control 
 signals is generated by executing a series of microcommands from the 
 control storage. Since the microprogram location counter can 
 be loaded from the processor as well as from the microcommand 
 register, this permits the microprogram sequence to be modified 
 by information from the processor, memory, or from the i/O as well 
 as by jump microcommands in the control storage. Refer to Figure 6. 
 
 The microprogrammed computer has two levels of stored 
 program control: 
 
 1. at the micro level using microcommands in the control 
 storage 
 
 2. at a macro level using instruction words in the main 
 memory to specify the operations performed by the 
 control unit 
 
81 
 
 Address From 
 Processor 
 
 
 Clock 
 
 
 
 < r 
 
 ,r 
 
 
 Microprogram Location 
 Counter 
 
 
 
 " 
 
 
 
 Control Program Storage 
 
 
 
 1 1 
 
 
 
 Micro command Register 
 
 
 
 1 
 
 
 
 
 I 
 
 
 — - 
 
 Decoder and Control 
 Pulse Generator 
 
 
 Control Signals To 
 Processor, Memory, I/O 
 
 Figure 6. Microprogrammed Control Unit Organization 
 
82 
 
 Since the control unit is programmable, it is possible to code 
 an entire application program at the micro level. The main memory 
 would contain no instructions as is the case wilh the MICRO 800. 
 It should be apparent that the programmable control unit gives 
 great flexibility not only for internal operations but also for 
 external I/O and control functions. This flexibility can be used to 
 great advantage in interfacing the computer to other equipment in a 
 system environment. Selecting the proper approach invariably derives 
 hardware cost savings in a system application. 
 
 11.2 Applications 
 
 There are five ways to approach application to system functions, 
 
 Each has its own advantages and disadvantages. 
 
 1. Micro level application programming- -Where maximum 
 throughput performance is required, the application can 
 be programmed directly with the microcommand set. All 
 commands are stored in read-only memory. The core 
 memory is used for storage of data and perhaps variable 
 parameters used to specify functional operations at the 
 micro level. This approach permits a direct processing 
 or control operation to be executed at each clock time. 
 One disadvantage is that the read-only memory program 
 cannot be altered. This problem can be solved by storing 
 variable control parameters in core memory. 
 
 2. Macro level programming using the standard software 
 level which may be more familiar than microprogramming. 
 Microprograms enable the small machine to simulate the 
 performance of another computer. By using some of the 
 read-only storage, the computer can be provided with a 
 repetoire of instructions. Throughput speed is sacrificed 
 in favor of greater flexibility in altering the application 
 program. Since macro instructions are not executed at the 
 same speed as the microcommands. (Diagnostics, Teletype 
 operating system) 
 
 3- Macro level programming using supplemental problem-oriented 
 macro instructions to enhance its performance and through- 
 put. These macro instructions are implemented by adding 
 special subroutines to the standard firmware in read-only 
 memory. (Convolutions, math algorithms, threaded list 
 operations, etc. ) 
 
83 
 
 i+. Macro level programming by emulation of another general- 
 purpose computer. Justification for this approach can 
 include: familiarity with another machine; an existing 
 investment in application software , availability of 
 specialized software programming aids. Using this approach, 
 the minicomputer is microprogrammed to execute instructions 
 of another computer directly from core memory without 
 prior language conversion. The i/O hardware is designed 
 when necessary to emulate the simulate system. An obvious 
 advantage to this approach is replacement of obsolete 
 hardware without sacrificing existing software. 
 
 5. Emulation of a special -purpose computer such as signal 
 processors, data compressors, telemetry de commutators. 
 
 11.3 Advantages of Microprogramming Performance in System Applications 
 
 While microprogramming can be used to derive significant 
 
 performance advantages over the fixed control computers, whether or 
 
 not full use needs to be made of this facility depends upon the 
 
 application. When a small-scale computer is applied in high-volume 
 
 situations, unit cost of hardware will usually far outweigh non-recurring 
 
 development costs. For a dedicated system application, spare capacity 
 
 computer performances is of no great value unless it can be used to 
 
 reduce hardware costs by absorbing additional system functions 
 
 into the internal time-shared logic. Here microprogramming can be 
 
 used to full advantage, and nominal one-time costs to develop 
 
 problem-oriented microprograms can result in significant reductions in 
 
 unit costs of hardware. 
 
 A fixed instruction set computer utilizes core-stored assembly 
 
 language subroutines to implement problem-oriented programs. Most of 
 
 these computers have a fixed word length compatible with core memory. 
 
 Isolated single precision arithmetic operations may be relatively fast. 
 
 Instruction execution times are dependent not only upon the core memory 
 
 cycle time but also by the operand addressing mode and other factors. 
 
8i4- 
 
 In the short word length machines, these limitations almost 
 always severely effect program execution speed. 
 
 A microprogrammed computer using a high-speed read-only 
 memory is particularly well suited where fast problem-oriented 
 operations are required. The basic data flow can be through 
 multiple file registers (hardware flip-flops) rather than core 
 memory. All basic information and data transfers are under 
 control of the high speed read-only memory through the file 
 registers. For many control applications, core memory is not 
 needed in the system, but can be added where buffering is 
 required for data or for the traditional software sequences. 
 Direct memory access can be employed for high-speed data. If 
 used for general purpose requirements, the core contains soft- 
 ware to address the macro held in read-only memory in such a 
 manner as to simulate a general purpose computer with an 
 instruction set and a word length defined by the microcommands 
 in the high-speed ROM firmware. 
 
 How fast is execution time of a microprogrammed computer? 
 Digital Scientific Corporation's META k has a 35 nsec ROM. The 
 microprogrammed computer can emulate fixed instruction set 
 computer but with some loss in speed for a comparable memory 
 cycle time. Memory efficiency is improved because of optimum 
 word length utilization. 
 
 Microprogram control simplifies most I/O interface 
 requirements, with the timing and buffering accomplished internally 
 without additional hardware or software. The firmware approach is 
 
85 
 
 less expensive than hardware control and can completely eliminate 
 the need for I/O software subroutines. High speed micro 
 operations often permit serial techniques to replace parallel 
 word handling to eliminate costly i/O buffers. 
 
 While memory efficiency is improved because of optimum 
 word length utilization, a significant speed pay-off occurs 
 when additional problem-oriented macros are added to a basic 
 instruction set. Multiple precision arithmetic and complex 
 macros which replace entire software subroutines in core can be 
 several times faster than software subroutines and yet require 
 only a small fraction of core memory allocation. 
 
 Many system problems can be solved initially by a conven- 
 tional software approach using a general purpose instruction set. 
 Augmenting this by problem-oriented macros has been noted. As 
 system requirements change, extra demands placed on the computer 
 may exceed any spare capacity in the machine. For such unexpected 
 situations, a fixed instruction set computer must be replaced 
 by a larger, more expensive machine—often at considerable cost in 
 engineering and system down time. With a microprogrammed computer, 
 more problem-oriented functions can be implemented in ROM to 
 improve system performance. These changes do not require replacing 
 the computer" a rather simple change or modification of ROM circuit 
 boards in the computer can create a dramatic gain in throughput 
 capacity. Software modifications are minimized since the macro 
 program is reduced rather than expanded by addition of the problem- 
 oriented instructions. 
 
86 
 
 LIST OF REFERENCES 
 
 "American Association of Collegiate Registrars and Admissions", Officers 
 Survey Report, 1965-66. 
 
 Bhushan, Abhay K., "Selecting a Small Computer For Your Application", 
 Computer Design, September, 1969* 
 
 "Educational Directions at the University of Illinois", A Report "by the 
 University Study Committee on Future Programs, January, 1963. 
 
 Finerman, Aaron, University Education in Computing Science, Academic Press, 
 New York and Londonj 1968. 
 
 Froehlich, G. J. and Carey, R. C, High Education Enrollment in Illinois 
 1969-2OOO, December, 1969. 
 
 IBM Feasibility Study for a Remote Terminal Central Computing Facility 
 
 Serving School and College Institutions, "Volume I : Functional 
 Requirements"; "Volume II: Preliminary Specifications", 
 International Business Machines Corporation, Data Processing Div., 
 112 East Post Rd., White Plains, New York 10601, 1967- 
 
 Lifton, Walter M., Educating for Tomorrow : The Role of Media, Career 
 
 Development, and Society, John Wiley and Sons, New York, 1970. 
 
 Margolin, Joe, "The Computer in Education: Whose Mission?", Educational 
 Technology, Vol. VIII, No. 124, December 30, 1968, pp. 9-12. 
 
 Minicomputers and Communications Preprocessors, "Part One: Minicomputers: 
 
 Concepts, Principles, and Applications"; "Part Two: Descriptions 
 of Individual Minicomputers Publications Division", Programming 
 Sciences Corporation, 6 East k^> Street, New York 10017, 1970. 
 
 Oettinger, Anthony C, Run Computer Run : The Mythology of Educational 
 
 Innovation, Harvard University Press, Cambridge, Massachusetts, 
 i~9S9T 
 
 "Progress Report of Determination of Enrollment Projections for 
 
 Institutions", Harvard University Press, Cambridge, Massachusetts, 
 1969. 
 
 "Projection of Enrollment in Institutions of Higher Learning in the State 
 of Illinois", University Bureau of Institutional Research, June, 
 1969. 
 
 Pierce, J. R., "Computers in Higher Education", Report of the President's 
 Science Advisory Committee, United States Government Printing 
 Office, Washington, D.C., 1967- 
 
87 
 
 Small Control Computers, Equity Research Associates, 55 Broad Street, 
 New York, New York 100CA-, 1969. 
 
 Suppes, Patrick, "The Uses of the Computer in Education", Scientific 
 American, No. 215, September, 1966, page 207- 
 
 Teichroew, Daniel, Major Decisions Regarding Computers in Colleges and 
 
 Universities, Case Institute of Technology, Cleveland, Ohio, 19^7' 
 
 "Volume 1. Management Information Services", Computerized Educational 
 Technology, P. 0. Box 5129, Detroit, Michigan £8236, 19^9- 
 
■$l % 
 
 tis*