Who Invented the Computer? Ben Gurley and the PDP-1

Who Invented the Computer? This is the nineteenth installment in our ongoing series.

In 1957, two engineers, Ken Olsen and Harlan Anderson co-founded Digital Equipment Corporation ("Digital") in a former wool mill in Maynard, Mass. Their original idea was to quietly carve a niche in the computing world by selling ready-to-use logic modules to computer labs.

The electronic modules (basic logic boards and flip-flops) made it easy for computer engineers to experiment with new technologies. Digital's market proved immediately profitable, and the company had no plans to do anything other than continue making and selling logic modules.

That is until a few of their engineers suggested the company began manufacturing their own line of computers. After all, Digital's logic modules were a significant component on new and existing computing machines.

Management pooh-poohed the idea on the basis that they did not want to compete with IBM and other computer giants — better to stay under the radar and continue selling logic modules. Fortunately for Digital, the engineering department refused to take no for an answer. They continued kicking ideas around and presenting them to higher ups.

Digital Builds Its Own Computer

Management was eventually won over and decided it was time to build a computer. But not one like every other company was producing. They wanted to focus the design of their machine on improving user interaction as opposed to just increasing the efficiency of processing, which is what the rest of the industry was focused on.

Management's goals for the device were that it be "user-interactive, small, affordable, exciting, and fun." To head up their project, Digital hired Ben Gurley away from MIT's prestigious Lincoln Laboratory. Gurley was the man responsible for design of the cathode tube display and light pen of the TX-0 computer.

Digital gave Gurley free rein as to the design of their machine, with the caveat that regardless of what he came up with, it was not to be called a computer. The marketing department feared their efforts to sell another computer would be swamped by the marketing efforts of the larger computer companies.

Using Digital's electronic models in combination with 2,700 transistors and 3,000 diodes, Gurley's team completed their machine within three and a half months. They named it the Program Data Processor, or as it quickly became known, PDP-1. Because of its size — a sleek 1,600 lbs. — many in the industry were soon referring to the PDP-1 as a "minicomputer."

A Computer for the User

The PDP-1 was an 18-bit word machine with lots of blinking lights on the console. It was slower and smaller than existing computers, but extremely user friendly. Peripherals included a large graphics display and a smaller high-resolution display, a multiplexed analog-to-digital converter for interfacing with lab equipment, actual audio output, a real-time clock, and a light pen — again, the focus was on user interactivity.

The PDP-1 also included a console electric typewriter with switches added to detect individual keypresses. While the device was prone to jamming, it did allow a user to do online debugging. Designed as a scientific machine, PDP-1 turned out to be much more. It led to a radical shift in computer design and is credited with opening the door to the era of minicomputers.

Not only was the PDP-1 the first computer to focus on user interaction above processing speed, but it also enabled more people to access computing power than ever before. Instead of renting a computer for $10,000 a month, the PDP-1 could be purchased by smaller businesses and computer labs for somewhere between $85,000 and $120,000.

A Mixed Legacy (and a Tragedy)

Although less than 50 PDP-1s were manufactured, they were the beginning of a successful line of minicomputers, eventually culminating in the widely popular, smaller, and more powerful PDP-8 and PDP-11 models. Digital would eventually sell more than 750,000 PDP models.

Digital ultimately replaced their PDP line with the VAX-11 series, a widely used 32-bit minicomputer able to perform many of the tasks done by large mainframe computers like the IBM System/370. During the 1980s, Digital became the second largest computer company in the world behind IBM and the largest private employer in Massachusetts.

Unfortunately, for Digital, more computer companies were stepping into the minicomputer arena, introducing ever smaller and more powerful machines and selling them for less. The company really began feeling the financial pressure of competition in the early 1990s and was eventually acquired by Compaq in June of 1998 — at that time, the computer industry's largest merger.

Tragically, PDP-1's creator, Ben Gurley did not live to see the industry-wide changes his machine would bring about. On Nov. 7, 1963, while Gurley was eating dinner with his wife and five children, a disgruntled former co-worker of Digital fired a rifle through Gurley's dining room window killing him instantly.