The Kenbak-1 - The World's First Personal Computer

The Kenbak-1 was created in 1971 by John V. Blankenbaker and recognized in 1986 as the world’s first “Personal Computer” by the Boston Computer Museum. This computer was designed before microprocessors were invented and consisted of small and medium scale integrated circuits mounted on one printed circuit board. I personally employed these computers at Nielsen Electronics College in the Electronics Technology Associates Degree program to familiarize Electronic Technicians with the operations and architecture of computers so they would be able to understand their duties if they became employed by main frame computer manufacturers or found work in industrial environments using the new “microprocessor” technology that was gaining momentum.

More information on the history of this amazing computer can be found online at the following resources:

This is my first hand, personal account of the Kenbak-1. A lot of people have displayed renewed interests in the first personal computers, but few can say they extensively taught and used them.



As best I can recall, it was somewhere around October or November of 1973, when I was contacted by CTI to inspect and advise them on a computer product they were considering. When I first saw the Kenbak-1, it made me very curious. It was a small blue box and it had a console. The console had push button keys, lights and a few switches. Unlike the other digital devices I encountered, there were no wires, other than the power cord. CTI explained that it was a “computer” and asked me if I would evaluate it for use in schools as a device to introduce students to computers and their internal programming requirements. I agreed and personally picked up the computer and training manual. In about a week, I was putting the small desktop sized computer through its paces. I was astonished at the “power” it contained!

Until the arrival of the Kenbak-1, all other devices I investigated for CTI could only perform a single step in the architecture of a “full blown” computer. As an example, using pre-wired computer “gates” consisting of And, Or, Nand, Nor, Exclusive-Or, etc., the technician would be required to assemble the “gates” via “jack-plug” wires, to make a complete digital circuit. Full adders – Half adders and small Arithmetic Registers could be assembled and tested. Lights on the console would confirm properly assembled circuits, or in some cases, voltmeters would give a (+) or (-) reading. As I recall, building the Central Processor Unit (CPU) was out of the question at the time. That particular kind of training allowed technicians to understand the components and electrical “sine waves” they would encounter in already manufactured “digital systems” but the technology could never emulate a completely assembled system.

Our “Digital Electronics Course” followed the normal instruction of the era and used stand-alone circuits. For familiarity, students would be taught Boolean Theorems, build “gates,” Half adders, Full adders and other simple digital circuits such as “seven segment” led numbering systems. Having a “lab” that could integrate those circuits into a complete system was out of the question until I examined the Kenbak-1 computer.

The Kenbak-1, had no “plug” wires, like most other trainers, and everything was concealed in the cabinet. In comparison to other digital or pseudo computer trainers, it looked rather “naked.”

The architectural design really caught my attention and it didn‟t take long to write a small program, using the Operation Codes in the manual. The manual also had an exhibit, explaining by “flow chart” how to input programs. I followed the “Operators Flow Chart” and was able to enter a simple “counting routine.” A counting routing is important, because it can be used to stop counting after a specific time lapse and generate an impulse that could cause some industrial function to become active. A simple example would be controlling “traffic lights.”

With the use of the manual, it was pretty easy to actually program the routine, enter it, read it back for accuracy, lock it in memory and upon pressing Start, run it. I thought the speed was excellent, considering the fact it was a “programmable computer.” The memory was sufficient to count up to 377 octal, or 256 binary and the sequence would start over. To state it lightly, I was amazed! When the Kenbak-1, was running, the console looked exactly like that of a Main Frame computer in action.

As I recall, I entered a number in memory, matched it and “branched/jumped” from the main routine into a subroutine to automatically stop the computer. Using the Console, I could verify the match visually. I also discovered I could modify or trouble shoot the program with ease because of its design. The Console permitted me to enter an Address in memory and display its contents visually on the Console lights. That included all the registers including the “Program Control Register.”

The computer allowed the programmer to predict the next instruction to be executed and it had a “Single Cycle” feature that sometimes was essential in troubleshooting programs. Of course, programmers would seldom be allowed to use that feature on Main Frame computers, however, Service Technicians frequently needed it. In my opinion, it would be a tremendous help to beginning programmers. I imagined later, as they gained experience, they would be using Print Outs of their complete programs with all kinds of computer-generated comments on improper Instruction Code to facilitate troubleshooting. When that happened, they would think they were in heaven compared to having to do it all through the console of the Kenbak-1. Making that change would be delightful and from the onset, they would know what the Print Out was, and how it was intended to be used.

The little computer‟s power was explored in depth and I became satisfied it had “programmable power.” Although the accompanying manual described many programs and provided the code for them, I preferred to write my own logic (flow chart) and code it. I was no stranger to the advantages of “Assembler Software” and “Compilers.” I designed a system for the Kenbak-1, that would allow for writing Symbolic Programs and manually supplying the Operational Codes and variables needed in the “housekeeping” steps. Because of me, the Kenbak-1, now had its first “Compiler.”

After coding, the programmer only needed to insert the actual code on the same line with the symbolic code. As any programmer knows, the use of Symbolic Programming prevents having to memorize the Mnemonic equivalent while working out the actual program. On the Kenbak-1, it meant a lot more. All the Mnemonic Instructions had to be further reduced to the “Absolute” Binary Code, prior to entering it into the computer. In other words, the computer was only programmable by inserting absolute Binary. All outputs were also in absolute. In my mind, the programmer could readily grasp the reason to submit the Symbolically Coded program to Card Punch Operators in preparation for having the computer do the compiling automatically and print, or punch out the complied program, ready to be corrected, processed against “test data” and “debugged.”

As I visualized it, the programmer‟s main concentration in learning the Main Frame computer would need to be on the “peripherals” attached to the computer and of course the Manufacturer‟s recommended Instruction Set. I also believed their Instruction Set would be easier to master, because the neophyte trained on the Kenbak-1, would have been introduced to many of them earlier. They would easily grasp the concepts of “dedicated memory buffers,” attachments such as a Printers, Automatic Card Punch Machines and Magnetic Tapes or Disc Drives as output devices. They would have experience with a Binary Output on the console of the Kenbak-1 that would reinforce learning the manufacturer‟s console. I‟m not indicating Binary Coded Decimal or Hexadecimal would not need to be further refined in the programmer‟s mind, only that it should be grasped more easily because of having exposure to Pure Binary or Octal on the Kenbak-1. When properly used, the “Hexadecimal” concept could also be demonstrated on the little computer.


Computer Manufacturers pride themselves on powerful instruction codes. To add power, they produced “Marco” instructions. These instructions were not normally “hard-wired” into the computer. They were included in the instruction set, but the Compiler program recognized them and produced a series of program instruction codes in the form of a small “Routine” that was added in every detail to the program being written. These small subroutines could allow for leaving the Main Routine, “memorize” the point it left, “Branch or Jump” to another routine, fully execute the Sub-Routine and automatically “return” to the place in the Main Routine it had left. Instructions of that nature prevented a need for “detailed” coding by a programmer. Macro‟s were designed by software programmers and were “pre-programmed” and usually a coding format meeting certain specifications were required. The little Kenbak-1 could simulate on a small scale how a Macro could do such functions!

After having the Kenbak-1, in my possession for about a week, I called a conference with the President of CTI to give my report. During that time, I explained they truly had a small copy of a Main Frame computer in their possession. The term, “Personal Computer” had not been coined yet. The only missing devices were “automatic data readers” and “automatic data output devices.” I explained what I considered to be “real” computer architecture the Kenbak-1 contained and asked if they would like to see me give a demonstration consisting of entering and running a program. They were extremely excited, and we arranged a time for the demonstration. In just minutes I had explained everything necessary for them to follow me as the program was entered, read back for accuracy, and “Run.”

I was so impressed with the Kenbak-1 that I promised CTI I would purchase it and implement it into the Electronics Program. They were surprised and asked why and how I intended to use it there. They were aware I was phasing out the Computer courses and wanted to know “where” I was going with the Kenbak-1, and why.


Because I wanted to assist CTI in marketing the Kenbak-1, I first I explained in detail that I thought the computer would be a highly desirable, “one on one” training device for teaching programmers in the very early stages of their training. To clarify that statement I further advised the Kenbak-1, was, in fact, a “real computer” and students in the early stages of learning to program, would find it very valuable as a training aid. It would assure programmers knew the Binary Code and how to Input data and read the console “lights” to examine the “Output” presented. In that connection, they would learn about internal storage and how information could be stored and manipulated within a real computer. Dedicated memory in the form of “buffers” would become evident to them. It would give students “hands-on experience” in using the Arithmetic Registers and demonstrate how they were needed to transfer data to storage for later use in making calculations, and of course, the “comparing” procedures and the resulting “switches” that would be set and later used in performing logical functions.

I acknowledged current text materials covered all of that, but it was theoretical and highly abstract in nature. I explained that the instructor teaching those things had to be highly qualified to be effective with a medium-sized class. By using the Kenbak-1, students would have the advantage of getting accustomed to the internal workings and procedures for programming a computer and avoid mistakes later on, as they began running their test programs on “full-blown” computers. Students with the proper “aptitude” would have little or no difficulty-absorbing computer programming concepts on the Kenbak-1.


Additionally, if CTI would follow my advice, I would provide them with a “Symbolic Coding Sheet, whereby the Kenbak-1, Instruction Set, could be manually coded against a flow chart and easily converted using manual techniques to Machine Code. That simple step would explain to students in a very personal way how the Software of a full-blown computer, could automatically take their coded program and make the conversion into Machine Readable Code for them. In other words the Kenbak-1, with little effort could teach them a lot about the devices they would need to use as they developed into competent programmers using commercially available programming materials. The work they would be doing on the Kenbak-1, could be related to any Main Frame computer on the market. Knowing the “Console” on the Kenbak-1, would greatly assist them when they encountered the “real thing.” In short, I envisioned the early programmer, “Flow Charting,” “Coding,” “Compiling,” entering and running several simple programs on the Kenbak-1, prior to taking up and wasting “valuable” time on the actual “Main Frame Computer” in their school or college.

The work they would be doing on the Kenbak-1, could be related to any Main Frame computer on the market. Knowing the “Console” on the Kenbak-1, would greatly assist them when they encountered the “real thing.” In short, I envisioned the early programmer, “Flow Charting,” “Coding,” “Compiling,” entering and running several simple programs on the Kenbak-1, prior to taking up and wasting “valuable” time on the actual “Main Frame Computer” in their school or college.


Unfortunately, CTI had their ideas on marketing the Kenbak-1. They wanted to concentrate on “High Schools” and use them as a market. Personally, I thought that would be a mistake. In my opinion, the High School teachers lacked the professional knowledge needed to teach the Kenbak-1. I reminded them that my experience with students coming into the Electronics Program from such schools were very weak in Basic Electronics and that in many cases, our Advanced Placement Tests, produced poor results.

I also explained that High Schools, had few “Out Come Evaluations” placed on the teachers of those courses and students were allowed to “skate by” many of the theoretical evaluations within the course. I warned CTI that based on

I warned CTI that based on experience we also noted students from those programs had very little knowledge of electronics test equipment. In the same breath, I explained student enrollments from High Schools into the Computer Science Programs knew very little, and in many cases, could not read Hollerith Code in punched cards! I was adamant they should try to market their exceptional product in courses beyond the High School level. CTI responded with the fact their existing sales people were highly entrenched in High Schools and that specific market was their forte. The management of CTI had their mindset. After that demonstration, I believe they were convinced to engage in business with John V. Blankenbaker the owner and inventor of the Kenbak-1. Later I was asked to put on a training seminar for a group of salesmen. It took time to schedule the sales staff, as

It took time to schedule the sales staff, as CTI was operating nationwide. Later, when the salesmen were all gathered up in Mt. Pleasant, South Carolina, I programmed a very simple “counting routine” into the Kenbak-1, for them. By that time, CTI had changed the name from Kenbak-1 to the CTI Digital Computer Systems Trainer – 5050. I explained many of its features and answered questions in detail. The next demonstration was taped on video by CTI. I remained with the salesmen long enough for them to enter their own counting routine and run it. In that meeting, the salesmen were ecstatic about having such a powerful training device available to them for marketing. I was invited to join them in a “celebration” at a local restaurant. The Kenbak-1, was the topic of conversation for hours. Later, CTI provided the salesmen with a copy of the video so they could practice at home with their Kenbak-1, Demonstrators.

I learned at the initial presentation with the CTI sales force, that their “job” of making a proper demonstration to educators was going to be difficult. Although they were extremely competent as electronic technicians, that, in no way qualified them to put on “understandable” computer presentations. Some salesmen had the necessary “aptitude” to program a simple problem into the computer and others didn‟t. It occurred to me that as they made their demonstrations, some educators would not have the required aptitude and fail to grasp the subject matter, others would catch on quickly, provided the salesmen did a good job in presenting it, and I had doubts they could. Drawing from my experience with IBM and their early understanding “Aptitude” was critical to their success I tried hard to influence CTI to be careful.


The Kenbak-1, was a small portable “Main Frame” and to fully comprehend it, one required the same programming aptitude needed by professional programmers. Because of my experience with hundreds of Computer Science Students, I assumed some salesmen and schoolteachers would be unable to grasp the necessary concepts. I was correct in that assumption. Because of the inability by educators to grasp the concepts, I believe their personal “job security” entered the picture and sales were inhibited because of that. Only forty were sold. Some of them were sold prior to CTI‟s involvement through magazine advertisements. Of the forty sold, I purchased eight from CTI.


My Kenbak-1, computers were not used to teach Computer Science. The college had NCR and IBM, Main Frame computers to accomplish that. The Kenbak-1s, were employed in the Electronics Technology Associates Degree program to familiarize Electronic Technicians with the operations and architecture of computers so they would be able to understand their duties if they became employed by main frame computer manufacturers or found work in industrial environments using the new “microprocessor” technology that was gaining momentum.

Once again, aptitude became a problem. Our electronics technicians were not screened for the necessity of a “programmers” aptitude. Most left with a small understanding of computers but that was sufficient to reinforce our “Digital Electronics” phase of the training. The Kenbak-1, gave them a chance to visualize all of the components, their connections to one another, timing, power supply, cooling system, etc.

The Kenbak-1, was a “staple” in the Electronics Degree program for many years because of the many features it contained and are still in use by modern computers. I paired up two students to a Kenbak-1. One student would have better aptitude than the other, and became an advisor to the less competent one. Using that system, each technician (pair) had a “dedicated” computer to program, troubleshoot and otherwise learn on. Remember, at the time, Main Frame Computers were extremely expensive – it was inadvisable to turn one of them over to student technicians.

The Kenbak-1, was a marvelous computer training aid. Not until companies like Heath Kit began to make PC computer-training devices was it discontinued. Even then, it was difficult to visualize the operations of the CPU in them. The Kenbak-1, had the ability to bring all data and registers to the front of the console. It could also be “Single Cycled.” In other words, each individual step in the computer could be executed and observed, one step at a time. Of course electronics was making a great change and later, “board swapping” would become the preferred method of troubleshooting.

Over the years and because of their frequent use our Kenbak-1 computers began to heat up. It appeared that because of the large quantities of small chips it was made up of, the heat generated was causing intermittent failure. We did notice Blankenbaker designed the “motherboard” with the chips separated from each other as far as possible, keeping with the small “desk top” design of the computer. Keep in mind these little computers were in use by us for many years. The chips were readily available off the shelf and when some failed, they were replaced but soon after, others failed too. We decided to increase the ventilation inside by drilling three small holes in the rear corners of the cabinet tops. That corrective measure was successful and the added circulation of air prevented any further chip failure.

The console had a row of “no bounce” keys, protruding from it. Entering programs or data was done by pushing “in” the key toward the metal plate making up the foundation of the console. For nimble fingers, the key action was extremely smooth and with some experience, programs were quickly entered. The contents of various registers could also be “Read.” The operator simply entered the address desired to be read, pressed “Read” on the console and the console “display lights” indicated what binary information was at the requested location.

Some students had a rather “heavy hand” when pressing in the “no bounce entry keys.” If one of them became broken, it was a very delicate task to remove and replace it, however we accomplished that feat until we ran out of “keys.” We experimented on one Kenbak-1, by replacing all of the keys with a no bounce toggle switch. It only toggled, when flipped down and it engaged only for a brief time. That machine is still in working order; however without the row of “black and white” keys, its character has changed. It‟s still a working model of the Kenbak-1, in all other aspects. The toggle switches appear to be more durable than the original keys. That modified Kenbak-1 is now in The First Computer Museum of Nova Scotia.

Electronic Technicians were programming “stop lights” using a Programmable Logic Array (Logic Gates built into a system whereby they could be connected, based upon the desired output) to perform the logic needed to sense automobiles in a reluctance loop, count the cars and determine the length of time to hold a light green, then “time” the caution light, turn it off, switch on and hold the red light “on” for a predetermined period of time and later return to the beginning only to repeat the process. Similar procedures were employed in factories to control industrial functions. Problems like this one were a natural for the Kenbak-1.


The Microprocessors for the most part were Medium Scale Integration. They had to be programmed in Absolute, but a Key Board (usually numeric) was available to enter the code. Technicians had to learn the basics of a computer‟s Central Processing Unit, (CPU). Memory had to be learned, as well as the “Instruction” and “Execute Cycle.” The feature for “Branching or Jumps” into Sub-routines and Registers, including Arithmetic Registers and Index registers needed to Alter Instruction within the program required understanding. The Computer Clock definitely needed to be learned and the Cycle Time to process specific instructions had to be fully comprehended to control precise timing routines. I quickly recognized the Kenbak-1, could simulate all those functions.

Understanding an “Output” and the variables under which a computer could provide one was required by technicians, because that would be the ultimate communications with the outside world. The Kenbak-1, was the perfect machine to learn about all those things. Exposure to the Kenbak-1, which is a combination of Medium and Small Scale Integration (MSI/SSI) provided enough for Electronic Technicians to get a grasp of the “stand alone” Medium Scale Integration (MSI) Micro that replaced “discrete circuit” logic consisting of transistors and in some cases vacuum tubes that were used where intense heat was a problem.

In usual cases the input to a Micro Computer is received in industrial applications from an external sensor. That was the equivalent of entering a “digit” via the console keys of the Kenbak-1. The low voltage “output” derived from the program in a Micro is then amplified and used to drive “mechanical relays” whereby high amounts of voltage/current may pass to “activate” heavy duty electrical motors, pneumatic or hydraulic devices to perform robotic tasks. The “output” lights emulated that function on the Kenbak-1. One may remember the Intel 8080. As time passed, Large Scale Integration improved the Micro‟s and various systems for entering code were developed. Now, we have a computer on a “chip.”

If one takes the time to analyze the power John Blankenbaker designed into his Kenbak-1, they would be truly amazed to learn he incorporated a complete computer with everything needed to process data, except speed, a larger memory, output signals to drive printers or otherwise record data on magnetic tape or discs. His output was by “lighted outputs” on the Console, which were great to get a “visual view” of the outcome of the programs action. Those output lights also gave the programmer an opportunity to see the code and make corrections, prior to entering it, and to “read back the program, step by step to assure accuracy.”

To prevent the program from being disturbed, the Kenbak-1, could “Lock” it in place. The only Input would then be the Variable Data needed to be “Fed” the program. That step is referred to as “housekeeping.” One had only to release the “lock” to perform that function. Once the program is entered, the Kenbak-1, performs all internal computing functions we use today, save the need for interrupts. Naturally, it is slow in speed because of the time it was built. Its limitation is only “memory,” “fast input” and “output to other devices.” In all other respects, it‟s a computer and it‟s small, portable, programmable and useful. At the time it was produced, it was an excellent “tool” to expose qualified students (those with aptitude) to computer technology, including the design, programming and operations of computers.


I also knew I had a big job ahead of me in preparing electronics instructors that had only worked with bits and parts of a computer to eventually learn all about it and teach it to my students. In order to facilitate the task of teaching the instructors, I set out to make the same demonstration for them I made for CTI and record it on video tape. To accomplish that, I developed all the needed items in advance, rehearsed and on a quiet Sunday morning went through the drill. My oldest son, Robert was in control of the video camera.

The rehearsal indicated he would need to keep the camera on the computer and my hands. At other times I would need to refer to written material and he was to focus on that and follow my “pointer.” Because of that technique all material used could be viewed. I would speak slowly, clearly and reemphasize as I felt it was needed. At the end of about 3 hours and two videotapes, we had captured the basics of operating and programming the Kenbak-1. The copyright was recorded in my son, David’s name, and if the Kenbak-1 is sold with this work as a package, he will release it to the new buyer.

The VHS was converted to DVD and the disc shown below has a “dim” but understandable presentation of the Kenbak-1, which takes 3 hours to view in its entirety. Scenes of Nielsen actually manipulating the computer console push buttons and visuals of the corresponding lights show up extremely well.

Digital Instructors would have a personal session with the Kenbak-1 and me and then be allowed to watch the video presentation. After that, they would have an opportunity to ask questions again. Eventually, they were required to solve the exact identical problem without the benefit of the video presentation or help from me. Once they passed that step of their training, they had to prove to me they could troubleshoot the computer. That entailed having to read the contents of memory locations to me, predict the next instruction to be executed, display the arithmetic register, change “constants” to lengthen the “loop” time and otherwise demonstrate they had a full understanding of what needed to be taught to students at a minimum.

Some instructors had never worked in an industrial environment and had to be shown how the Kenbak-1 could be used to simulate Microprocessors. I normally accomplished that by “talking” them through simple industrial functions and explaining how the small voltage from activated sensors provided “input” to the micro and after processing the input against other variables, it could produce an “output.” Hypothetically, the output would engage electronic circuits or relays outside of the computer to perform specialized industrial tasks. I also asked them to emphasize that some micros could take more than one input and through programming, make tests of the inputs and make more complicated decisions for various industrial processes. The use of outputs would be basically the same. Further, they must explain to students the “output” of one micro, could easily be the “input” to another and further “processing” would be required to perform or not to perform a certain industrial function.


CTI bought out the Kenbak-1 and immediately changed its name to the Digital Computer Systems Trainer “5050” (fifty- fifty). They didn‟t make any design changes other than place their CTI label in place of the word Kenbak on front of the computer. The training manuals published by the Kenbak Corporation, were modified and all reference to the Kenbak Corporation was removed. Again, CTI renamed the training manuals to conform to the new name for the Kenbak-1. In 1974, a copyright was established on the Programming Reference Manual, P-5050, and the Student Laboratory Manual, H-5050. The first printing for CTI was March, 1974. When CTI went out of business, Nielsen Electronics purchased all copyrighted material. When the Kenbak-1 was “pulled” from the curriculum at the school, I exercised my rights and placed the Kenbak-1, and all associated material in my possession as personal property.

Appendix I consists of the written material used by students to perform the minimum course requirements in the Electronics Technology Course, using the Kenbak-1 (CTI Model 5050).

The “sleeve” of this publication contains a DVD that was copied from the very old training tapes to train the Nielsen Electronics Institute instructors. It will also parallel the printed material used by students. I gave the original old training videotapes to be displayed alongside the Kenbak-1, computers I sold to The First Computer Museum of Nova Scotia. I also provided them with the DVD and suggested they set up a TV and use a “push and play” system so visitors could see the Kenbak-1 in action.

Appendix II, consists of a copy of the electronic schematics for the Kenbak-1. There are no indications they belong to either the Kenbak-1 or the CTI 5050, however they are authentic copies of the electronics incorporated into the computer. They were used in troubleshooting the Kenbak-1 by my school expert, Mr. Gary Crozier, as aging problems arose. It‟s noteworthy that I gave the originals to be displayed alongside the Kenbak-1, computers I sold to the First Computer Museum of Nova Scotia. The curator of that museum promised he would allow colleges and universities access to the Kenbak-1 and all printed material I supplied him. He would set up a “loaner” system and as equipment was returned, it would be shipped to other interested schools.

Appendix III, consists of the CTI published, Programmers Reference Manual, P-5050. Researchers are encouraged to examine this text material as it explains in depth, the Addressing Modes, Instructions and Register-to-Register Operations. Some of these functions were not covered in depth on the video presentation.

Appendix IV, consists of the CTI published, Student Laboratory Manual. It contains 30 student exercises. The video presentation covers many of the instructions and techniques used throughout the 30 student exercises.


In order to establish when I purchased my first Kenbak –1, I used the Inventory Records published by the school CPA. Those records indicate it went into inventory and began to depreciate in 1973.


I had an excellent working relationship with CTI. When they got their shipment of Kenbak-1, materials in, (1973) there were about eight or ten fully assembled Kenbak –1 computers, several PC cards (the term mother board was not coined at the time), Console face plates, complete with input keys, output lights and switches, completely wired and ready to attach to the mother board. Back panel, power supplies were complete with the fan in place, also ready for attachment to the PC card by a simple plug connection. There were numerous, blank PC cards, front Console plates, fans, assorted “sleeves” of Integrated Circuits, the tops and bottoms of pretty blue cabinets, shiny steel handles, “spacers,” screws, bolts and the little rubber “feet” which would eventually be attached to the bottom of the Kenbak-1. Everything was present to put a Kenbak-1 together. It appears John V. Blankenbaker sold out to CTI and that included everything, “lock stock and barrel.” In any event, CTI gained control of it. After CTI closed its doors, I had control and owned the copyrighted material.


I feel very strongly that because some of the Kenbak-1 computers were fully assembled, John V. Blankenbaker, its inventor, personally put them together. If such is the case, I consider them invaluable. In September 2003, I sold seven (7) Kenbak-1 computers to The First Computer Museum of Nova Scotia and retained one for myself. I firmly believe all Kenbak-1 computers in existence were built by John Blankenbaker or his helpers. I‟m absolutely certain CTI never built a Kenbak-1, computer from scratch. I also do not believe they sold any, other than to me.


I was present when CTI was working on a “jig” to attach components on a blank motherboard, but the project was never completed. I also had an opportunity to view their production concept. Their plan was to develop the “jig” and apply a specific methodology for soldering the correct components into the proper place. Later the supervisor would train production line employees how to do the same job. When I was examining the manufacturing procedure, the supervisor had the electronic schematics at her side, assorted “sleeves” of chips and a small “stack” of PC Cards devoid of components. In spite of my efforts to assist in marketing, the salesmen failed to convince educators to purchase the Kenbak-1 and the manufacturing project was never brought to fruition by CTI. Because the electronics field was advancing very rapidly, the older, Philco Ford training devices were fast becoming obsolete. Heathkit was entering the training market with professional “breadboard” trainers, completely supported with student manuals. They offered, Direct Current, Alternating Current, Semi-Conductor

Because the electronics field was advancing very rapidly, the older, Philco Ford training devices were fast becoming obsolete. Heathkit was entering the training market with professional “breadboard” trainers, completely supported with student manuals. They offered, Direct Current, Alternating Current, Semi-Conductor laboratories and manuals. The labs would support Basic, Advanced, and Digital circuits. It became obvious to me that without an infusion of more advanced electronic training equipment, CTI was destined to go out of business – and they did. However, that has nothing to do with the performance of the Kenbak-1. It was dong a fine job for the capable instructors, and me, whom I taught its “power” to. We had a job to train Electronic Technicians about computers, and we did, oblivious to the fact we were also using the world‟s first personal computer to do it! Amazingly, it served its purpose into the mid 1990‟s.


Unknown to CTI they had acquired the world‟s first “Personal Computer,” Kenbak-1. As time has proven, no one knew the Kenbak-1, was the first Personal Computer until, 1986! Only when the Boston, Computer Museum started a contest to determine exactly what early computing device could be considered the world‟s first personal computer, was the mystery unraveled. According to, “The Computer Museum Report, Volume 17 – Fall 1986, advertisements went out worldwide from October 1985 to March 1986, designed to solicit old machines for the purpose of analyzing them and measuring them against pre-determined standards specifically developed to make such a determination. According to the report, the heading of the ad ran – “Wanted: Old Thinker-toys.” Offers flooded them from 13 countries, vying for recognition.

The report indicated that over 320 entries were received. A panel of judges using previously prescribed criteria analyzed each entry to determine if it qualified as a Personal Computer. A total of 137 items were reportedly accepted. The judges were, according to the report, Stephen Wozniak, designer of the Apple II and co-founder of Apple Computer, David Bunnell, an early MITS employee, current publisher (1986) of PC World, and Oliver Strimpel. (Oliver Strimpel is specifically included, as he referred to himself in the report I‟m referencing). Only after searching worldwide did they make their decision that the Kenbak-1, designed, built, and marketed by, John V. Blankenbaker in 1971, through his California based, Kenbak, Corporation, qualified as the “world‟s first personal computer.” Nielsen Electronics Institute had already been using the little computer for about 13 years when that announcement was made!

Very little was published in that report about the Kenbak-1, and John V. Blankenbaker has been serenely silent about his accomplishments. I hope the material presented here will further enhance his status and his remarkable invention. I am honored to have spoken and written to him about the Kenbak-1. The information he provided to me is considered invaluable and hopefully, one day, he will amplify more on his background.

I‟ve tried hard to provide a comprehensive history of the Kenbak-1, when it was actually used by students, in a highly productive way as they earned the Associates Degree in Electronics Technology at Nielsen Electronics Institute. Its use in my school is the only known instance where the Kenbak-1 was integrated into a technological curriculum offered commercially to train students in a school or college. Because its design matched the conventional design, of mainframe computers as well as Micro Processors, the Kenbak-1 was kept in constant usage for many years and hundreds, if not thousands of students were trained on it. In that connection, I feel qualified to state:

“I pioneered the use of the world‟s first personal computer and placed the first microprocessor “styled” emulator in the hands of electronics technicians.”

In other words, I pioneered the use of a microprocessor into an electronics training program.

Anyone that has not fully investigated the design of the Kenbak-1, will never understand, or come to the full realization of the accomplishment John V. Blankenbaker made when he designed and produced it. One must keep in mind as the Kenbak-1, is explored, that it was designed and built using Small to Medium Scale Integration – the microprocessor as we know it today had not yet fully “bloomed.”


Without the advantage of using a microprocessor chip, John V. Blankenbaker designed and installed on a Printed Circuit card (PC card), the complete computer, save the power supply and input/output devices used on the console. He accomplished this extraordinary feat in 1971 and began to market the world‟s first personal computer. Between The Kenbak Corporation and CTI only about 40 computers were sold. Simply because only forty computers were sold is no indication the Kenbak-1, was a failure. On the contrary, “computer wise” it was extremely effective and was used for over 20 years in my Junior College. Nielsen Electronics Institute. Because so little is published about the Kenbak-1, I felt it necessary to explain it in depth. Computer Science has indeed gone past me and admittedly by John, but history demands his accomplishments not be set aside! In the future, scientists and researchers will want to study this early material involving Personal Computers and the advances they have made. John has provided the first “foundation” for PCs and Nielsen Electronics Institute proved it was “rock solid.”


To my knowledge, Nielsen Electronic Institute was the only Junior College or for that matter the only school, to effectively use the Kenbak-1, as a learning tool for programming or to enhance the understanding of Main Frame computers and the actual visualization and use of “solid state” memory, arithmetic, index and instruction registers, during the execution and instruction cycles of programs, by electronic technicians. The latter was because the Kenbak-1, could be “Single Cycled” and by proper use of the console, the contents of every instruction, memory cell or register could be visualized by bringing it up, either from Registers or Memory on the output lights. It‟s truly a miraculous machine. Sometimes, I wonder what Bill Gates could have done with it, had he been made aware of its power.


Although there has been no indication the following assumption would be true, I‟m sure if the Kenbak-1, had been successfully marketed, John V. Blankenbaker would have eventually sold attachments for it and it would have become more user friendly to further enhance its use in classrooms. The attachments I speak of would have been a “Ten Key” pad to enter data that would have been converted to binary code, later an “Alpha-Numeric” keyboard and a small “Dot Matrix” printer to capture “output.” I know a lot about the aggressive nature of CTI Education Products, Inc. I‟m certain had the profit potential they hoped for been realized, they would have most certainly made those enhancements to it.


I‟ve been in contact with the inventor by telephone and Email. When I asked John if I was correct and his design emulated a Main Frame Computer he wrote, stating that, “Not in speed. Except for the lack of interrupts, it could be compared to much larger computers. The memory was very small and the speed was very slow.” In my mind, I had to ask, “what more could John have hoped for, considering the fact his computer was built from chips available off the shelf?” John also stated, “I designed the Kenbak-1, from scratch by myself.” He also indicated he still had a set of the original schematics. The PC board was magnificent in its design and John shared the fact it was also his design. Everything inside the cabinet was a perfect fit. There was space above and below the PC motherboard to allow air to circulate for cooling. The power supply was attached to the back panel and a fan, also attached to it assured the components were kept cool. Its Console was the front panel. The design was amazing. Only a small amount of space was required for students to use the Kenbak-1, and refer to the training manual at the same time.
Unfortunately, the concept was so new educational salesmen could not convince schools and colleges to implement it for teaching “Computer Concepts” or “Programming.” There is no doubt in my mind, had the Kenbak-1, been a success, schools and colleges over the United States would have produced “Computer Literate” graduates much earlier than actually happened. In my personal opinion, “Educators” missed an excellent opportunity to provide their students with “computer backgrounds” earlier because of their unwillingness or “mental” inability to work their way through the Kenbak-1. IBM used signs and they had a simple logo that appeared everywhere. It was only one word, “THINK.” I miss those signs even today and wish they would reappear!


Because the Kenbak-1, is “architecturally” sound, I realized as time passed, it would have historical value. I also knew the sales of them were extremely limited and surmised because of teachers and or students using them without the necessary aptitude, many would be discarded. When I removed them from our curriculum, I also exercised my option and transferred them from the school to myself personally. When I decided to close the Junior College in 1999, I pulled them off the storage shelf along with schematics, some training books, and the videos, still in their plastic cases and stored them in my garage in a large “boat box” specifically purchased for that purpose. Each time I moved, the big box moved with me. They were not well packed and I believe some of the “no bounce” keys got damaged in the moves. In a trial run of all the computers, only one was actually working. Because the console “keys” are the only way to “input” a program, a broken or loose key prevents any further testing. I started to re-attach some of the keys with super glue, but decided that should be done by an expert, possibly in the restoration section of a museum.


A Kenbak-1, was first placed in the Boston Computer Museum and it has since been transferred to The Computer History Center in California. I sold seven of my Kenbak-1‟s to The First Computer Museum of Nova Scotia. Some were in working order, others were not. Those nine Kenbak-1, computers are the only ones I know of on public display. They are extremely rare because only forty (40) were built. Of those built, I now control only one. Fortunately for me, when CTI went out of business, I purchased the training manuals, schematics and some pieces and parts. I also bought the right to all of their copyrights.


I gave The First Computer Museum of Nova Scotia the original schematics of the Kenbak-1 to put on display in the museum. I kept a copy for my own use and consider it my personal property. I also provided the original “Electronic Technician” training materials, used to demonstrate most of the programming functions I‟ve described earlier for them to put on display. I kept the copies and also consider them to be my personal property. In both cases, the copies were more presentable than the originals because of their aging. I also gave them one of the earliest “Digital Trainers” made by Philco Ford. That is truly a treasure. There were two “video cases” containing materials I videotaped for the CTI Salesmen. I instructed the owner of the museum to have them opened, cleaned, copied and copies returned to me. The originals in the case could be put on display in the museum if he desired. As yet I have not received my copies. I had the original videotape I used to train my instructors, taken apart and recopied. The original was given to the museum for the purpose of putting it on display also. The Digital Video Disc (DVD) I made from my original videotape was provided to the museum and it‟s allowed to be “played” within the museum. I still consider all printed and video material to be my personal intellectual property. Much of it will be incorporated in this autobiography.


In addition to the copies contained in the Boston Computer Museum and the First Computer Museum of Nova Scotia, there may be three copies in circulation. Mr. John Blankenbaker indicated in a telephone call I made to him (year 2000) that his Daughter had reported she heard a Kenbak-1, was sold on E-Bay for $3,000. There have been other sales reported to me. In one case a Kenbak-1 was sold for $2,000. In talking with the seller, it appeared he didn‟t know its worth and when he got a $2,000 offer he accepted it. Later I was told one sold on Ebay for $20,000 but I could not get confirmation of that sale. Notwithstanding those already mentioned, other than the one in my possession, I don‟t know of any others. When I was talking with John, I asked him if he had any computers, he stated it might be possible for him to put a copy together from some parts he had stored somewhere, however he indicated he now had other interests and his time and investment in the Kenbak-1, was wasted. In later years he contacted me asking for a “console” light. He built a complete computer for his son except for one of the Console Lights. I‟m sure he found one and completed it. If I‟m correct there would only be a little over a dozen in existence.


I praised the little computer to John. He acknowledged that other “programmers” really liked his invention and expressed an interest in it, just as I had. But he informed me his computer wasn‟t designed for experienced programmers, it was designed to “teach students” how to program. The fact other programmers liked it didn‟t impress him – it appeared he was disappointed it could not be sold in quantities to educational institutions, to teach people about computers, which was his ultimate goal.

I got the distinct impression from him that he himself would have been an excellent educator in “Computer Science.” Because so many years had passed when I was conferring with him, he indicated the computing industry had passed him by with technological advances. His main interest was now in the Genealogy of his ancestors and he was devoting all his time to building a Blankenbaker web site.

In the same telephone call I asked him to: “Please write your autobiography as there is definitely a place in history for it.” He replied, “Bob, I‟m only 70 years old. I‟ll do that when I‟m too old to work on my other interests.” I chuckled at that thought and we soon ended the conversation. Now, I‟m 77 and feel just about the same way! Unless John reads this story, he probably doesn‟t know how valuable an asset his little computer was to my Junior College and the students that had an opportunity to be trained on it. They would number in the high hundreds, and perhaps over a thousand.