© Mark Ollig
In 1970, John Blankenbaker founded the Kenbak Corp. in Los Angeles, CA, and envisioned manufacturing an affordable, easy-to-use home computer.
In the spring of 1971, before the first microprocessor chip had been invented, Blankenbaker finished constructing his prototype computer, the Kenbak-1.
Since his computer had no central processor, it relied on digital and sequential logic gates to execute arithmetic and logical tasks.
The memory comprises two streams of 1,024-bit serial sequential access memory (SAM) for 2,048 bits, which equals 256 bytes since there are eight bits in a byte.
The Kenbak-1 had a clock cycle time of one microsecond, comparable to the clock speed of a 1 MHz microprocessor.
There was no keyboard; the computer used switches to key the input, and lights displayed the output.
The Kenbak-1 computer uses machine code to write programs and performs less than 1,000 instructions per second, as each operation requires multiple clock cycles, and accessing the memory takes up a lot of time.
The Kenbak-1 computer made use of binary base-two arithmetic.
From a set of front panel switches, input data was entered for the machine code instruction set. The output was then displayed through a row of individual lights.
The Kenbak-1 was an eight-bit machine using a basic instruction set, making it suitable for simple educational and hobbyist purposes.
The computer measured 4.25 by 19.25 by 11.5 inches, and it weighed approximately 13.5 pounds.
The Kenbak-1 lacked pre-installed programs, so a user manual included sample programs a person could input and execute on the computer.
On Jan. 16, 1972, the News Chronicle newspaper in Thousand Oaks, CA, featured John Blankenbaker instructing computer programming, generally taught at the college level, to fifth and sixth-graders.
Blankenbaker taught students how to convert long binary numbers into shorter written forms using the base-eight octal and base-16 hexadecimal numbering systems.
I recall in 1979 when my brother Mike and I used binary, octal, and hexadecimal conversions to program the first digital telephone system in Winsted installed at the local hospital.
Each student had a Kenback-1 computer on their desk and used its console buttons to enter instruction programs.
The students entered instruction data into the Kayback-1 computer using its switches and buttons and then executed the program by pressing the start button.
The Kenbak-1 would then begin its operation of the input instructions, and the output results were displayed as a combination of illuminated lights.
After executing each programming instruction, the lights updated to display the results.
The newspaper noted how one student used the Kenbak-1 to calculate the trajectory of a model rocket.
Grade school students 52 years ago learned the basics of writing, programming, and running computer programs on the Kenbak-1.
In mid-1973, the Kenbak Corporation closed its doors after selling only 44 computers.
During a June 14, 2007 interview, Blankenbaker said, “We didn’t choose the right market, we should have emphasized the private individual.”
Although sales of the Kaybak-1 were unsuccessful, in May 1986, a panel of judges at the Computer Museum in Boston, MA, recognized the Kenbak-1 as “the first personal computer.”
One of the panel judges was Apple computer co-founder Steve Wozniak.
Today, only 14 Kenbak-1 computers are known to be owned by collectors and museums.
In 1980, Timothy Paterson wrote the disk operating system (DOS), initially called the quick and dirty operating system (QDOS), for Seattle Computer Products (SCP) to work with the Intel 8086 microprocessor.
The name reflects the approach used by Paterson to build a functional operating system as quickly as possible, as QDOS was to be only a temporary OS until the completion of the CP/M-86 (Control Program for Microcomputers Model 86) OS to be used with the Intel 8086 processor-based computers.
QDOS evolved into 86-DOS, used as an operating system with computers among early computer hobbyists.
Around 1980, IBM requested Microsoft to provide an operating system (OS) for its new IBM personal computer (PC).
In 1981, Microsoft bought 86-DOS from SCP and hired Tim Paterson to modify the software design into MS-DOS (Microsoft Disk Operating System), licensed to IBM for its computer OS, called PC-DOS.
PC-DOS and MS-DOS were widely used operating systems for computers with very few distinguishable differences.
On Aug. 12, 1981, IBM launched its computer, the IBM Personal Computer (model 5150), initially priced at $1,565, which today amounts to $5,112.
The model 5150 computer I used was equipped with an Intel 8088 4.77-MHz CPU, 64 KB of RAM, two 160 KB 5.25-inch (floppy) disk drives, a monochrome display, an IBM Model F keyboard, an Epson MX-80 dot-matrix printer, and a 20 MB external hard drive the size of a bread box.
The computer came with pre-installed software, including PC-DOS, a text-based operating system; IBM BASIC, a programming language; VisiCalc, a spreadsheet; and MultiMate, a word processor.
In 1994, the IBM Personal Computer model 5150 I used for many years while working at the telephone company in Winsted, was donated to the local high school.
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IBM Personal Computer model 5150 |
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John Blankenbaker with the Kenbak-1 |
