ENIAC

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ENIAC on a picture of the US Army, in the foreground Betty Holberton , in the background Glen Beck
Programmers Jean Jennings (left) and Frances Bilas Spencer (right) work on the ENIAC control panel at the Moore School of Electrical Engineering in 1945.

The Electronic Numerical Integrator and Computer ( ENIAC ) was the first powerful electronic universal computer . It served the US Army to calculate ballistic tables .

history

On behalf of the US Army , ENIAC was developed from 1942 by John Presper Eckert and John William Mauchly at the University of Pennsylvania and presented to the public on February 14, 1946.

Mauchly and Eckert founded a computer company, Eckert-Mauchly Computer Corporation , in 1946 , which was later taken over by Remington Rand . A patent was applied for in 1947, and long-term legal proceedings began in 1967 to determine its validity. They led to the fact that the patent was declared invalid in 1973 because of the properties already known from the Atanasoff-Berry computer (ABC); since Mauchly had an opportunity to study the ABC during a visit to Atanasoff in 1941, and probably drew some inspiration from it, the ENIAC was considered a derivative work by the court. The fame for inventing the first electronic computer, which Mauchly and Eckert had shared until then, has since passed to Atanasoff.

In 1947, ENIAC moved from Philadelphia to the nearby Ballistic Research Lab in Aberdeen. ENIAC was shut down on October 2, 1955.

Technical specifications

Similar to the Atanasoff-Berry computer (1938–1942) and the British Colossus (1943), a special cryptographic computer, the ENIAC used electron tubes to represent numbers and electrical pulses for their transmission. This resulted in a significantly higher computing power than that of Konrad Zuse's Z3 (1941), which had a more modern architecture , but was still based on electromechanical relays . Like the ASCC (built between 1939 and 1944, later known as "Mark I"), ENIAC used a decimal system to represent numbers.

The ENIAC consisted of 40 parallel working components, each of which was 60 cm wide, 270 cm high and 70 cm deep. The entire system was built in a U-shape, took up an area of ​​10 m × 17 m and weighed 27 tons. It consisted of 17,468 electron tubes, 7,200 diodes , 1,500 relays, 70,000 resistors and 10,000 capacitors . The power consumption consisted of 80 kW for the heating, 40 kW for the tube currents and 20 kW for the fans; the anode and screen grid power was limited to 25% of the maximum value. The construction of ENIAC cost US $ 468,000 - an amount that was only available due to the high demand for computing power on the part of the US Army (corresponds to a current value of approximately US $ 7,330,000). Compared to its predecessors, the ENIAC already impresses with its size.

A big problem in the development of the ENIAC was the susceptibility of the electron tubes to errors. If only one of the 17,468 tubes failed, the entire machine calculated incorrectly. In order to keep the costs of these inevitable failures low, special diagnostic programs were built into the ENIAC to make it easier to find a tube to be replaced. One countermeasure was to install stronger tubes than you actually needed and to operate them with only about 25% of their rated power. It was also noticed that more tubes were broken when switching on and off than during operation. As a consequence, it was decided not to switch off the ENIAC anymore. The downtime could be reduced to a few hours per week.

Skills

The ENIAC could add, subtract, multiply, divide and take square roots.

An addition / subtraction took 0.2 milliseconds, a multiplication up to 2.8 ms, a division up to 24 ms and a square root more than 300 ms.

How the ENIAC works

The basic component for the function of the ENIAC was the accumulator , which could store a 10-digit signed decimal number as well as add and subtract it. Each of the 20 accumulators could perform such a calculation in 0.2 milliseconds. This time interval is also known as the addition cycle. Two accumulators can be interconnected for calculations with double precision.

Other arithmetic components were the multiplier (three copies) and the divider / square rooter. A multiplier implemented a multiplication table, according to which a subroutine was controlled that ran on four accumulators. A multiplication took up to 2.8 milliseconds (depending on the length of the numbers). The divider / square rooter was constructed in a similar way, which required up to 65 milliseconds (13 addition cycles per digit) for a division or square root. The programming of complex calculations was possible with the Master Programmer (two copies), which allowed recursive programming.

The initiating unit was responsible for starting the system. When the ENIAC was switched on, the flip-flops assumed random values ​​so that the components were in an undefined state. With a special program of the initiating unit, the flip-flops could be brought into a defined state, and z. B. the accumulators are initialized with 0. The initiating unit also had a start button with which an ENIAC program was started manually. The cycling unit served as the clock generator and supplied the other components with control pulses via static cables. It could also be switched to a step-by-step mode that made troubleshooting easier.

programming

The ENIAC was programmed by connecting the individual components with cables and setting the desired operations on rotary switches. The ENIAC was programmed by women, the "ENIAC women": Kay McNulty , Jean Bartik , Betty Holberton , Marlyn Wescoff , Frances Bilas and Ruth Teitelbaum . You had previously done ballistic calculations on mechanical desktop computers for the military .

“At the University of Philadelphia, ballistic tables were calculated on behalf of the army - primers for the artillery that recorded the trajectory of the various projectiles for guns. The calculation was done by hand, the only help was a tabulating machine that could multiply and divide. The employees who did the math were called after their job - computers, the calculators. "

The components of the ENIAC were statically connected to each other in order to receive the clock pulses of the cycling unit. There were other static connections between the cooperating components (e.g. between a multiplier and the 4 allocated accumulators). All other connections for running a program had to be made manually. For the transmission of program pulses there were cables running horizontally at foot height in program trays, for number pulses the digit trays were used at head height. There were sockets on trays and components into which cables could be plugged.

A clear architectural disadvantage of the ENIAC was the lack of an instruction memory. The Z1 , Z3 and the Mark I already read their commands from a punched tape , while the ENIAC had to be rewired for each program. According to John von Neumann's ideas , the ENIAC was converted into a computer with an instruction memory in 1948 . This slowed down his computing power to 1/6, but the duration of the reprogramming was also reduced, so that an overall time gain was achieved.

Data output

The constant transmitter (consisting of three components) and the function tables (three components, three copies each) served as read-only memories . The former was mainly used to control a punch card reader . On the latter, 104 ten-digit decimal numbers (although only six digits can be set individually) were stored with an access time of five addition cycles. Calculation results could also be printed: A punch card printer could be controlled via the printer panel (consisting of three components).

An immediate visual output was integrated in the accumulators: In the upper area of ​​the component there were 102 glow lamps to display the currently stored number (ten each for each of the ten digits, two for the sign ).

Cultural influence

On the occasion of the first public presentation of ENIAC in February 1946, a halved table tennis ball was placed over each lamp - a design that was the model for many of the computers that followed and that set the style for science fiction at the time .

Comparison with other early computers

Computer model country Installation Floating point
arithmetic		 Binary Electronically Programmable Mighty Turing
Zuse Z3 Germany May 1941 Yes Yes No Yes, using punched tape Yes, without any practical use
Atanasoff-Berry computer USA Summer 1941 No Yes Yes No No
Colossus UK 1943 No Yes Yes Partly, by rewiring No
Mark I. USA 1944 No No No Yes, using punched tape Yes
Zuse Z4 Germany March 1945 Yes Yes No Yes, using punched tape Yes, without any practical use
around 1950 Yes Yes No Yes, using punched tape Yes
ENIAC USA 1946 No No Yes Partly, by rewiring Yes
1948 No No Yes Yes, using the resistor matrix Yes

Replicas and simulators

ENIAC on a chip, University of Pennsylvania (1995) - Museum of Computer History

In 1996, the University of Pennsylvania funded a project called " ENIAC-on-a-Chip " in honor of ENIAC's 50th anniversary , which produced an integrated circuit with the same functionality and dimensions of 7.44 mm × 5.29 mm. Although this chip with a clock frequency of 20 MHz calculated many times faster than the jubilee and therefore cannot be considered a true-to-original replica, the computing speed was only a fraction of that of contemporary PCs from the late 1990s.

On June 2, 2004, a project that has been in operation since 2003 at the Free University of Berlin was completed, which ENIAC simulates as a Java applet on conventional PCs in the web browser. For this purpose, practical instructions were published in June 2006, which ENIAC programs as a modulo computer .

literature

  • JP Eckert Jr., JW Mauchly, HH Goldstine, JG Brainerd: Description of the ENIAC and Comments on Electronic Digital Computing Machines . Moore School of Electrical Engineering, University of Pennsylvania, 1945.
  • HH Goldstine, A. Goldstine (1946): The Electronic Numerical Integrator and Computer (ENIAC) . In B. Randell (Eds.): The Origins of Digital Computers , Springer-Verlag (1982).
  • Herman Lukoff, From Dits to Bits: A personal history of the electronic computer , Robotics Press, Portland, Oregon 1979
  • J. Van der Spiegel, JF Tau, TF Ala'ilima, and LP Ang (2000). The ENIAC: History, Operation and Reconstruction in VLSI . In R. Rojas (Eds.): The First Computers; History and Architectures , MIT Press.
  • Arthur W. Burks: Electronic Computing Circuits of the ENIAC . Proceedings of the IRE, pp. 756-767, August 1947.

Web links

Commons : ENIAC  - album with pictures, videos and audio files

The ENIAC programmers

  • The ENIAC programmers. Project Women in the History of Information Technology , University of Bremen, Frauen-informatik-geschichte.de
  • ENIAC Programmers , Women in Technology International (WITI) Hall of Fame (English)

Individual evidence

  1. ↑ Steve Lohr: Jean Jennings Bartik, a Computer Pioneer, Dies at 86 . ( nytimes.com [accessed October 8, 2018]).
  2. ↑ Patent US3120606 : Electronic numerical integrator and computer. Filed June 26, 1947 , published February 4, 1964 , applicant: Sperry Rand Corporation, inventor: John Presper Eckert, Jr.; John W. Mauchly. ‌
  3. ↑ Arthur W. Burks: Electronic Computing Circuits of the ENIAC . Proceedings of the IRE, pp. 756-767, August 1947.
  4. ↑ This figure was based on the template: Inflation determined, rounded to a full $ 10,000 and relates to the previous January.
  5. ↑ Jennifer S. Light: When Computers Were Women . In: Technology and Culture , 40.3, 1999
  6. ^ Jamie Gumbrecht: Rediscovering WWII's female "computers" . CNN , February 2011
  7. ↑ When computers were female . In: Süddeutsche Zeitung TECHNIK, 41/2015
  8. ↑ Replica of the ENIAC on a chip. Archived from the original on August 5, 2020 ; accessed on August 5, 2020 .
  9. ↑ Simulation of the ENIAC. Archived from the original on January 15, 2020 ; accessed on January 15, 2020 (English).
  10. ↑ Programming example of the modulo function. Archived from the original on May 29, 2013 ; accessed on May 29, 2013 (English).
This version was added to the list of articles worth reading on December 24, 2005 .