Today the phone in your pocket weighs a few hundred grams. In 1946 the machine that came to mind at the words "electronic computer" weighed about 30 tons and took up an entire room. Its name was ENIAC, and it is remembered as the first general-purpose electronic computer.
Born as a wartime project
ENIAC was designed for the US Army's Ballistic Research Laboratory. Its purpose was to calculate artillery firing tables: long calculation charts showing where a shell will land when fired at a given angle. Calculated by hand, these tables could take weeks.
The machine was designed by John Mauchly and J. Presper Eckert at the University of Pennsylvania's Moore School of Electrical Engineering. ENIAC was announced to the public on the evening of February 14, 1946 and officially unveiled the next day, February 15, 1946. That's why you may see both dates in sources.
A giant in numbers
According to Penn Engineering, ENIAC filled a room of about 9 x 15 meters (30 x 50 feet). Seen from the front, its 40 panels formed a "U" shape about 24 meters long.
Inside were about 18,000 vacuum tubes, around 6,000 relays according to Wikipedia, 70,000 resistors, 10,000 capacitors and roughly 500,000 solder joints. It drew about 150 kilowatts of electricity and had its own power lines. Its weight is usually given as "30 tons"; Wikipedia notes that these are 30 short tons, about 27 metric tons.
Its speed was incredible for its time, too. It could do 5,000 simple additions or subtractions per second. According to Penn, it finished a ballistic calculation that took 12 hours by hand in about 30 seconds. That is roughly a 1,440-fold speedup.
The vacuum tubes did the job of today's transistors: switches that turn electric current on and off. But each one heated up like a light bulb, took up space and could fail over time. ENIAC's enormous size and high energy consumption came largely from the sum of these thousands of glass tubes.
| ENIAC (1946) | Today |
|---|---|
| About 30 tons | A phone weighing a few hundred grams |
| 40 panels filling a room | A device that fits in your palm |
| 18,000 vacuum tubes | Billions of transistors on a single chip |
| 5,000 additions per second | Billions of operations per second |
| About 150 kW of power | A battery of a few watts |
Six women programmers
The part of ENIAC overlooked longest was the people who ran it. The machine had no keyboard or programming language in today's sense. Programming meant rearranging cables and switches by hand. To solve a new problem the machine practically had to be "rewired" from scratch.
The first team that did this work consisted of six women: Kay McNulty, Jean Jennings (Bartik), Betty Snyder (Holberton), Marlyn Wescoff, Frances "Fran" Bilas and Ruth Lichterman. Penn today remembers them as the "ENIAC Six" and lists their names one by one, with their married surnames. Although the names of those who designed the machine always come first, it was these six programmers who really made it "talk".
The start of an era
According to Wikipedia, these six women were well-trained mathematicians with math education, chosen from among the "computer" teams (human calculators) that calculated firing tables with desk calculators. There were no programming languages yet; by studying ENIAC's diagrams and physical structure, they worked out for themselves how to use the switches and cables. Some of the first steps of today's software engineering were taken in this room full of cables.
One of ENIAC's first real programs was not firing tables but a feasibility study for a thermonuclear weapon. It served the Army for about nine years and spent part of its life at the Aberdeen Proving Ground. In 1955 it gave way to newer machines such as EDVAC and ORDVAC.
The story of ENIAC has two dates, two designers and six programmers; but the real hero may be the idea itself. It showed concretely that electronic circuits could calculate many times faster than human hands. The next generation of computers moved toward storing the program in memory instead of in cables, and things became far more flexible.
This 30-ton giant is considered a distant ancestor of every computer we use today. The shift from room-filling tubes to chips that fit in a pocket took only a few human lifetimes.
Do you think someone looking at our computers 80 years from now will see them the way we see ENIAC?