The Atanasoff–Berry Computer (ABC) was the first electronic

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 digital

Digital

A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

 computing

Computing

Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...

 device. Conceived in 1937, the machine was not programmable, being designed only to solve systems of linear equation

Linear equation

A linear equation is an algebraic equation in which each term is either a constant or the product of a constant and a single variable....

s. It was successfully tested in 1942. However, its intermediate result storage mechanism, a paper card writer/reader, was unreliable, and when inventor John Vincent Atanasoff

John Vincent Atanasoff

John Vincent Atanasoff was an American physicist and inventor.The 1973 decision of the patent suit Honeywell v. Sperry Rand named him the inventor of the first automatic electronic digital computer...

 left Iowa State College

Iowa State University

Iowa State University of Science and Technology, more commonly known as Iowa State University , is a public land-grant and space-grant research university located in Ames, Iowa, United States. Iowa State has produced astronauts, scientists, and Nobel and Pulitzer Prize winners, along with a host of...

 for World War II assignments, work on the machine was discontinued. The ABC pioneered important elements of modern computing, including binary arithmetic and electronic switching

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 elements, but its special-purpose nature and lack of a changeable, stored program distinguish it from modern computers. The computer was designated an IEEE Milestone in 1990.

Atanasoff and Clifford Berry

Clifford Berry

Clifford Edward Berry was an American inventor.Clifford Berry was born in Gladbrook, Iowa to Fred Gordon Berry and Grace Strohm...

's computer work was not widely known until it was rediscovered in the 1960s, amidst conflicting claims about the first instance of an electronic computer. At that time, the ENIAC

ENIAC

ENIAC was the first general-purpose electronic computer. It was a Turing-complete digital computer capable of being reprogrammed to solve a full range of computing problems....

 was considered to be the first computer in the modern sense, but in 1973 a U.S. District Court invalidated the ENIAC patent and concluded that the ENIAC inventors had derived the subject matter of the electronic digital computer from Atanasoff (see Patent dispute).

Design and construction

According to Atanasoff's account, several key principles of the Atanasoff–Berry Computer (ABC) were conceived in a sudden insight after a long nighttime drive during the winter of 1937–38. The ABC innovations included electronic computation, binary arithmetic, parallel processing

Parallel processing

Parallel processing is the ability to carry out multiple operations or tasks simultaneously. The term is used in the contexts of both human cognition, particularly in the ability of the brain to simultaneously process incoming stimuli, and in parallel computing by machines.-Parallel processing by...

, regenerative capacitor memory

Regenerative capacitor memory

Regenerative capacitor memory is a type of computer memory that uses the electrical property of capacitance to store the bits of data. Because the stored charge slowly leaks away, these memories must be periodically regenerated Regenerative capacitor memory is a type of computer memory that uses...

, and a separation of memory and computing functions. The mechanical and logic design was worked out by Dr. Atanasoff over the next year. A grant application to build a proof of concept

Proof of concept

A proof of concept or a proof of principle is a realization of a certain method or idea to demonstrate its feasibility, or a demonstration in principle, whose purpose is to verify that some concept or theory that has the potential of being used...

 prototype was submitted in March, 1939 to the Agronomy

Agronomy

Agronomy is the science and technology of producing and using plants for food, fuel, feed, fiber, and reclamation. Agronomy encompasses work in the areas of plant genetics, plant physiology, meteorology, and soil science. Agronomy is the application of a combination of sciences like biology,...

 department which was also interested in speeding up computation for economic and research analysis. $5,000 of further funding to complete the machine came from the nonprofit Research Corporation

Research Corporation

The Research Corporation for Science Advancement is an organization in the United States devoted to the advancement of science, funding research projects in the physical sciences. It was also a major supporter of the research that led to the presentation of Interlingua in 1951...

 of New York City

New York City

New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

.

The ABC was built by Dr. Atanasoff and graduate student Clifford Berry

Clifford Berry

Clifford Edward Berry was an American inventor.Clifford Berry was born in Gladbrook, Iowa to Fred Gordon Berry and Grace Strohm...

 in the basement of the physics building at Iowa State College during 1939–42. The initial funds were released in September, and the 11-tube prototype was first demonstrated in October, 1939. A December demonstration prompted a grant for construction of the full-scale machine. The ABC was built and tested over the next two years. A January 15, 1941 story in the Des Moines Register

Des Moines Register

The Des Moines Register is the daily morning newspaper of Des Moines, Iowa, in the United States. A separate edition of the Register is sold throughout much of Iowa.-History:...

announced the ABC as "an electrical computing machine" with more than 300 vacuum tubes that would "compute complicated algebraic equations" (but gave no precise technical description of the computer). The system weighed more than seven hundred pounds (320 kg).and was 800 square feet (74.3 m²) in all. It contained approximately 1 mile (1.6 km) of wire, 280 dual-triode vacuum tube

Vacuum tube

In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...

s, 31 thyratron

Thyratron

A thyratron is a type of gas filled tube used as a high energy electrical switch and controlled rectifier. Triode, tetrode and pentode variations of the thyratron have been manufactured in the past, though most are of the triode design...

s, and was about the size of a desk.

It was not a Turing complete computer, which distinguishes it from more general machines, like contemporary Konrad Zuse

Konrad Zuse

Konrad Zuse was a German civil engineer and computer pioneer. His greatest achievement was the world's first functional program-controlled Turing-complete computer, the Z3, which became operational in May 1941....

's Z3 (1941), or later machines like the 1946 ENIAC

ENIAC

ENIAC was the first general-purpose electronic computer. It was a Turing-complete digital computer capable of being reprogrammed to solve a full range of computing problems....

, 1949 EDVAC

EDVAC

EDVAC was one of the earliest electronic computers. Unlike its predecessor the ENIAC, it was binary rather than decimal, and was a stored program computer....

, the University of Manchester designs, or Alan Turing

Alan Turing

Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...

's post-War designs at NPL and elsewhere. Nor did it implement the stored program architecture that made practical fully general-purpose, reprogrammable computers.

The machine was, however, the first to implement three critical ideas that are still part of every modern computer:

1. Using binary
   Binary numeral system
   The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...
   
    digits to represent all numbers and data
2. Performing all calculations using electronics
   Electronics
   Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
   
    rather than wheels, ratchets, or mechanical switches
3. Organizing a system in which computation
   Computation
   Computation is defined as any type of calculation. Also defined as use of computer technology in Information processing.Computation is a process following a well-defined model understood and expressed in an algorithm, protocol, network topology, etc...
   
    and memory
   Computer storage
   Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
   
    are separated.

In addition, the system pioneered the use of regenerative capacitor memory

Regenerative capacitor memory

Regenerative capacitor memory is a type of computer memory that uses the electrical property of capacitance to store the bits of data. Because the stored charge slowly leaks away, these memories must be periodically regenerated Regenerative capacitor memory is a type of computer memory that uses...

, as in the DRAM

Dram

Dram or DRAM may refer to:As a unit of measure:* Dram , an imperial unit of mass and volume* Armenian dram, a monetary unit* Dirham, a unit of currency in several Arab nationsOther uses:...

 still widely used today.

The memory of the Atanasoff–Berry Computer was a pair of drums, each containing 1600 capacitor

Capacitor

A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...

s that rotated on a common shaft once per second. The capacitors on each drum were organized into 32 "bands" of 50 (30 active bands and 2 spares in case a capacitor failed), giving the machine a speed of 30 additions/subtractions per second. Data was represented as 50-bit binary fixed point numbers. The electronics of the memory and arithmetic units could store and operate on 60 such numbers at a time (3000 bits).

The AC

Alternating current

In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 power line frequency of 60 Hz

Hertz

The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

 was the primary clock rate for the lowest level operations.

The arithmetic logic functions

Arithmetic logic unit

In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...

 were fully electronic, implemented with vacuum tubes. The family of logic gates ranged from inverters to two and three input gates. The input and output levels and operating voltages were compatible between the different gates. Each gate consisted of one inverting vacuum tube amplifier, preceded by a resistor divider input network that defined the logical function. The control logic functions, which only needed to operate once per drum rotation and therefore did not require electronic speed, were electromechanical, implemented with relay

Relay

A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...

s.

Although the Atanasoff–Berry Computer was an important step up from earlier calculating machines, it was not able to run entirely automatically through an entire problem. An operator was needed to operate the control switches to set up its functions, much like the electro-mechanical calculators and unit record equipment

Unit record equipment

Before the advent of electronic computers, data processing was performed using electromechanical devices called unit record equipment, electric accounting machines or tabulating machines. Unit record machines were as ubiquitous in industry and government in the first half of the twentieth century...

 of the time. Selection of the operation to be performed, reading, writing, converting to or from binary to decimal, or reducing a set of equations was made by front panel switches and in some cases jumpers.

There were two forms of input and output: primary user input and output and an intermediate results output and input. The intermediate results storage allowed operation on problems too large to be handled entirely within the electronic memory. (The largest problem that could be solved without the use of the intermediate output and input was two simultaneous equations, a trivial problem.)

Intermediate results were binary, written onto paper sheets by electrostatically modifying the resistance at 1500 locations to represent 30 of the 50 bit numbers (one equation). Each sheet could be written or read in one second. The reliability of the system was limited to about 1 error in 100,000 calculations by these units, primarily attributed to lack of control of the sheets' material characteristics. In retrospect a solution could have been to add a parity bit to each number as written. This problem was not solved by the time Atanasoff left the university for war-related work.

Primary user input was decimal, via standard IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

 80 column punched card

Punched card

A punched card, punch card, IBM card, or Hollerith card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions...

s and output was decimal, via a front panel display.

Function

The ABC was designed for a specific purpose, the solution of systems of simultaneous linear equations. It could handle systems with up to twenty-nine equations, a difficult problem for the time. Problems of this scale were becoming common in physics, the department in which John Atanasoff worked. The machine could be fed two linear equations with up to twenty-nine variables and a constant term and eliminate one of the variables. This process would be repeated manually for each of the equations, which would result in a system of equations with one fewer variable. Then the whole process would be repeated to eliminate another variable.

Patent dispute

J. Presper Eckert

J. Presper Eckert

John Adam Presper "Pres" Eckert Jr. was an American electrical engineer and computer pioneer. With John Mauchly he invented the first general-purpose electronic digital computer , presented the first course in computing topics , founded the first commercial computer company , and...

 and John Mauchly

John Mauchly

John William Mauchly was an American physicist who, along with J. Presper Eckert, designed ENIAC, the first general purpose electronic digital computer, as well as EDVAC, BINAC and UNIVAC I, the first commercial computer made in the United States.Together they started the first computer company,...

 were the first to patent a digital computing device, the ENIAC

ENIAC

ENIAC was the first general-purpose electronic computer. It was a Turing-complete digital computer capable of being reprogrammed to solve a full range of computing problems....

. The ABC had been examined by John Mauchly in June 1941, and Isaac Auerbach, a former student of Mauchly's, alleged that it influenced his later work on ENIAC, although Mauchly denied this (Shurkin, pg. 280-299). In 1967 Honeywell

Honeywell

Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....

 sued Sperry Rand in an attempt to break their ENIAC patents, arguing the ABC constituted prior art

Prior art

Prior art , in most systems of patent law, constitutes all information that has been made available to the public in any form before a given date that might be relevant to a patent's claims of originality...

. The United States District Court for the District of Minnesota

United States District Court for the District of Minnesota

The United States District Court for the District of Minnesota is the Federal district court whose jurisdiction is the state of Minnesota. Its two primary courthouses are in Minneapolis and Saint Paul...

 released its judgement on October 19, 1973, finding in Honeywell v. Sperry Rand

Honeywell v. Sperry Rand

Honeywell, Inc. v. Mc'Donalds., et al. 180 USPQ 673 was a landmark U.S. federal court case that in April 1973 invalidated the 1964 patent for the ENIAC, the world's first general-purpose electronic digital computer, thus putting the invention of the electronic digital computer into the public...

that the ENIAC patent was a derivative of John Atanasoff's invention. The decision was not appealed.

Campbell-Kelly and Aspray conclude:
The case was legally resolved on October 19, 1973 when U.S. District Judge Earl R. Larson held the ENIAC patent invalid, ruling that the ENIAC derived many basic ideas from the Atanasoff–Berry Computer. Judge Larson explicitly stated, "Eckert and Mauchly did not themselves first invent the automatic electronic digital computer, but instead derived that subject matter from one Dr. John Vincent Atanasoff".

Replica

The original ABC was eventually dismantled, when the University converted the basement to classrooms, and all of its pieces except for one memory drum were discarded. In 1997, a team of researchers led by John Gustafson

John Gustafson (scientist)

John L. Gustafson is an American computer scientist and businessman, chiefly known for his work in High Performance Computing such as the invention of Gustafson's Law, introducing the first commercial computer cluster, measuring with QUIPS, leading the reconstruction of the Atanasoff–Berry...

 from Ames Laboratory

Ames Laboratory

Ames Laboratory is a United States Department of Energy national laboratory located in Ames, Iowa. The Laboratory conducts research into various areas of national concern, including the synthesis and study of new materials, energy resources, high-speed computer design, and environmental cleanup...

 (located on the Iowa State campus) finished building a working replica of the Atanasoff–Berry Computer at a cost of $350,000. The replica ABC is now on permanent display in the first floor lobby of the Durham Center for Computation and Communication at Iowa State University. It is currently on loan to the Computer History Museum

Computer History Museum

The Computer History Museum is a museum established in 1996 in Mountain View, California, USA. The Museum is dedicated to preserving and presenting the stories and artifacts of the information age, and exploring the computing revolution and its impact on our lives.-History:The museum's origins...

 in Mountain View, California

Mountain View, California

-Downtown:Mountain View has a pedestrian-friendly downtown centered on Castro Street. The downtown area consists of the seven blocks of Castro Street from the Downtown Mountain View Station transit center in the north to the intersection with El Camino Real in the south...

 for a major exhibition

External links

• The Birth of the ABC
• Rebuilding the ABC
• John Gustafson, Reconstruction of the Atanasoff-Berry Computer
• The ENIAC patent trial
• Honeywell v. Sperry Rand Records, 1846-1973, Charles Babbage Institute
  Charles Babbage Institute
  The Charles Babbage Institute is a research center at the University of Minnesota specializing in the history of information technology, particularly the history since 1935 of digital computing, programming/software, and computer networking....
  
  , University of Minnesota.