ENIAC
In June 1941, John Mauchly stood before a stack of Friden calculators at the University of Pennsylvania. He watched graduate students manually compute artillery firing tables for the U.S. Army Ordnance Department. The process was slow and prone to human error. Mauchly wondered if electronics could replace these mechanical devices. He partnered with J. Presper Eckert, an electronics expert who lacked Mauchly's mathematical background. Together they drafted a plan for an all-electronic calculating machine in August 1942. The U.S. Army accepted their proposal and awarded a six-month research contract worth $61,700. Construction began secretly under the code name Project PX in July 1943. Herman Goldstine oversaw the project for the government while assembly started in June 1944. The team completed the conception of the computer by September 1944. Final construction finished in May 1945, followed by testing at the Moore School.
By 1956, ENIAC contained 18,000 vacuum tubes and 7,200 crystal diodes inside its massive frame. The machine weighed more than 30 tons and occupied roughly 1,800 square feet of floor space. It consumed 150 kilowatts of electricity during operation. Numbers were stored using ten-position ring counters that required 36 vacuum tubes per digit. Arithmetic operations relied on counting pulses generated by these ring counters. The system featured 20 accumulators capable of holding ten-digit decimal numbers. These units could perform 5,000 simple addition or subtraction operations per second. A special multiplier unit handled up to 385 multiplication operations each second. Another divider and square rooter unit managed approximately 40 division operations per second. Engineers reduced tube failures from daily occurrences to one failure every two days after 1948. The longest continuous run without a single error lasted 116 hours in 1954.
Herman Goldstine selected six women from a pool of about 200 female computers at the Moore School. Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas, and Ruth Lichterman became the primary operators. They studied blueprints and physical structures to manipulate switches and cables since no programming languages existed yet. These women determined how to input programs into the machine while developing an understanding of its inner workings. Their expertise made their positions difficult to replace with returning soldiers after World War II ended. Despite having professional degrees in mathematics, they were designated subprofessionals rather than professionals. Men with similar education received the title of professional while these women performed the actual work. They narrowed bugs down to individual failed tubes that technicians could then replace. Later research by Kathryn Kleiman revealed that most programmers were not invited to the ENIAC's 50th anniversary event. Kleiman tracked them down to record oral histories and released a book on their contributions in 2022.
ENIAC ran its first rough version of thermonuclear weapon calculations during December 1945 and January 1946. The machine correctly showed that Edward Teller's initial hydrogen bomb scheme would not work. This result led Teller and Stanislaw Ulam to develop a new design together. John von Neumann became aware of ENIAC one year into the three-year project. He used the computer to calculate thermonuclear reactions using equations for Los Alamos National Laboratory. Scientists involved in nuclear bomb development utilized massive groups of human computers to investigate neutron travel distances. Von Neumann realized ENIAC's speed allowed these Monte Carlo method calculations to be done much faster. The success of this project demonstrated the value of Monte Carlo methods in scientific research. A press conference held on the 1st of February 1946 announced the completed machine to the public. Elizabeth Snyder and Betty Jean Jennings developed the demonstration trajectory program that calculated missile paths in 15 seconds.
The original contract amount was $61,700 but the final cost reached almost $500,000. ENIAC shut down on the 9th of November 1946 for refurbishment and memory upgrades before moving to Aberdeen Proving Ground in 1947. It operated continuously until 11:45 p.m. on the 2nd of October 1955 when retired in favor of EDVAC and ORDVAC computers. In March 1948 a converter unit enabled programming through standard IBM cards from the reader. This modification reduced reprogramming time from days to hours despite cutting speed by a factor of six. An early 1952 high-speed shifter improved shifting operations by five times. July 1953 saw the addition of a 100-word expansion core memory using binary-coded decimal representation. New Function Table selectors and pulse-shaping circuits supported this expanded memory system. Three new orders were added to the programming mechanism to accommodate these changes. The machine remained in continuous operation at Aberdeen until its retirement date in late 1955.
John Mauchly examined the Atanasoff-Berry Computer prototype built by John Atanasoff and Clifford Berry in June 1941. He applied for an electronic digital computer patent in 1947 which was granted in 1964 as US Patent 3,120,606. A landmark federal court case Honeywell Inc v Sperry Rand Corp voided this decision in 1973. The ruling stated that ENIAC inventors derived subject matter from Atanasoff's work. It gave legal recognition to Atanasoff as the inventor of the first electronic digital computer. This decision placed the invention of the electronic digital computer into the public domain. The patent battle involved disputes over rights between Eckert and Mauchly and their former university administrators. Oral history interviews with Carl Chambers and S. Reid Warren discussed these patent disputes extensively. The outcome ensured that no single entity could claim exclusive ownership over the foundational concepts of electronic computing.
Common questions
When was the ENIAC computer officially announced to the public?
A press conference held on the 1st of February 1946 announced the completed machine to the public. Elizabeth Snyder and Betty Jean Jennings developed the demonstration trajectory program that calculated missile paths in 15 seconds.
Who were the six women programmers who operated the ENIAC computer?
Herman Goldstine selected Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas, and Ruth Lichterman as the primary operators. These women studied blueprints and physical structures to manipulate switches and cables since no programming languages existed yet.
What happened to the ENIAC patent rights in 1973?
A landmark federal court case Honeywell Inc v Sperry Rand Corp voided this decision in 1973. The ruling stated that ENIAC inventors derived subject matter from Atanasoff's work and gave legal recognition to Atanasoff as the inventor of the first electronic digital computer.
How much did the final cost of building the ENIAC reach compared to the original contract?
The original contract amount was $61,700 but the final cost reached almost $500,000. This discrepancy arose during construction which began secretly under the code name Project PX in July 1943.
When did the ENIAC computer finally retire from operation?
It operated continuously until 11:45 p.m. on the 2nd of October 1955 when retired in favor of EDVAC and ORDVAC computers. The machine remained in continuous operation at Aberdeen until its retirement date in late 1955.