Nepedia
Back to Discover
Advanced Reader
💻

Atanasoff–Berry computer

technology Maturity 11-13 Next article →

The Atanasoff–Berry computer, or ABC, was the first automatic electronic digital computer. It was a groundbreaking machine that changed how we use electricity for math. While modern computers can do almost anything, the ABC was a special-purpose machine. It was designed specifically to solve systems of linear equations. These complex math problems were very important for physics research. The ABC is considered a major milestone because it introduced several ideas we still use. These include binary arithmetic and electronic switching.

Atanasoff Berry Computer
Atanasoff Berry Computer

To understand how the ABC worked, we must look at its unique components. It used vacuum tubes to perform arithmetic calculations. A vacuum tube is an electronic device that controls the flow of electricity. Before the ABC, machines used slower mechanical parts like wheels or telephone relays. By using tubes, the ABC could calculate much faster than its predecessors. The machine also featured a specialized arithmetic logic unit, or ALU. This part of the computer performed the actual math operations. The ALU operated on one bit of each number at a time. It even kept the carry or borrow bit in a capacitor for the next cycle.

Memory was another vital part of the ABC's design. It used a system called regenerative capacitor memory. This memory consisted of two large drums that rotated on a single shaft. Each drum contained 1,600 capacitors to store data. These drums rotated once every second. The capacitors were organized into 32 bands, with 30 bands being active. Two extra bands were kept as spares in case a capacitor failed. This setup allowed the machine to perform 30 additions or subtractions per second. The electronics could store and operate on 60 numbers at once.

Atanasoff-Berry add-subtract module.agr
Atanasoff-Berry add-subtract module.agr

The history of the ABC began with a sudden moment of inspiration. In the winter of 1937–38, Professor John Vincent Atanasoff had a breakthrough. This happened after a long nighttime drive to Rock Island, Illinois. He worked at Iowa State College to bring his ideas to life. He was joined by a graduate student named Clifford Berry. They built the machine in a basement between 1939 and 1942. To fund the project, they received $5,000 from the Research Corporation of New York City. The machine was successfully tested in 1942.

Despite its brilliance, the ABC had several technical limits. It was not a programmable machine. This means it could not follow a new set of instructions for different tasks. It also lacked a stored-program architecture. This type of architecture was not implemented until the Manchester Baby in 1948. The machine also required a human operator to manage its functions. An operator used front-panel switches and jumpers to set up the work. The machine also used a paper card reader for input. For intermediate results, it used a paper card writer. This system was not perfect and had an error rate of about one in 100,000 calculations.

The ABC's legacy was hidden for many years due to legal battles. For a long time, many believed the ENIAC was the first electronic computer. The ENIAC was created by John Mauchly and J. Presper Eckert. However, a major patent dispute changed this understanding. In 1973, a U.S. District Court ruled on the case of Honeywell v. Sperry Rand. The court invalidated the ENIAC patent. The judge concluded that the ENIAC designers had derived their ideas from Atanasoff. This legal decision helped the world rediscover the importance of the ABC.

Display inside of rest stop at mile 100 northbound on I-35 in Iowa, Commemorating the ABC Computer
Display inside of rest stop at mile 100 northbound on I-35 in Iowa, Commemorating the ABC Computer

Today, we recognize the ABC as a foundational piece of technology. In 1990, it was officially designated an IEEE Milestone. While the original machine was dismantled in 1948, its impact remains. Researchers even built a working replica of the ABC in the late 1990s. This replica cost $350,000 to complete. You can still see honors for this invention in Iowa today.

The ABC connects the era of mechanical calculators to the era of modern digital computing. It proved that vacuum tubes could make math incredibly fast.

663 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (4)
File:Atanasoff Berry Computer.gif
Atanasoff Berry Computer.gif
File:Atanasoff-Berry add-subtract module.agr.jpg
Atanasoff-Berry add-subtract module.agr.jpg
File:Display inside of rest stop at mile 100 northbound on I-35 in Iowa, Commemorating the ABC Computer.jpg
Display inside of rest stop at mile 100...
File:Outside wall of rest stop at mile 100 northbound on I-35 in Iowa, Commemorating the ABC Computer.jpg
Outside wall of rest stop at mile 100...
More to explore

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.