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ENIAC Computer- Everything You Need To Know

Hi there! Let me walk you through the fascinating history of the groundbreaking ENIAC computer. I‘ll provide plenty of details and analysis so you can fully appreciate this pioneering achievement in electronics and computing.

Overview: ENIAC – The First General-Purpose Electronic Computer

The Electronic Numerical Integrator and Computer (ENIAC) was the world‘s first programmable, general-purpose electronic digital computer. Developed in secret during World War II, ENIAC represented a huge leap forward in computing technology when it was unveiled in 1946.

Though primitive by today‘s standards, ENIAC‘s launch marked the transition from calculating devices using mechanical parts or manual processes to fully electronic computing. It demonstrated the feasibility of high-speed digital computation using vacuum tubes and anticipated the microelectronics revolution that followed.

So what made ENIAC special? Let‘s look at some key facts:

  • Could be programmed to solve many types of numerical problems, not just one specific function
  • Used electronic circuits for high-speed calculation and data processing
  • Relied on vacuum tubes for digital logic instead of mechanical parts
  • Could perform 5,000 additions/subtractions per second, a huge increase in speed
  • Was enormous in size, weighing 30 tons and taking up 1,800 square feet

ENIAC‘s origins, design, and adoption reflect the intersecting needs of World War II-era mathematics, military efforts, and the emerging electronics industry.

Next, we‘ll delve into the historical backdrop that made this ambitious project possible.

Wartime Origins of the ENIAC

World War II created a pressing need for advanced computing capabilities to help Allied forces gain advantages in vital areas:

  • Cryptanalysis – breaking enemy codes and ciphers was crucial for intelligence efforts. The Colossus computers in Bletchley Park were built to analyze the German Enigma machine.
  • Ballistics – calculating accurate firing tables for unprecedentedly large guns and complex shell trajectories required speed.
  • Nuclear weapons – performing equations for shock wave propagation, explosive lenses and other nuclear physics challenges depended on fast, programmable computers.
  • Weather forecasting – long-range forecasts relying on differential equations supported strategic planning and operations.

ENIAC emerged from the ballistics calculation demands. The Moore School of Electrical Engineering at the University of Pennsylvania had been working on specialized firing table computers since 1940.

In 1943, the U.S. Army signed a contract with the Moore School to build an electronic calculator for artillery settings. Physicist John Mauchly and electrical engineer J. Presper Eckert led the project, collaborating with a skilled team of engineers and technicians.

After years of intense, classified development, ENIAC was completed in late 1945. The next year, it was unveiled to the public, astonishing people with its electronic speeds and programmability.

ENIAC‘s Groundbreaking Technology

For its time, ENIAC possessed remarkable capabilities:

  • 5,000 additions/subtractions per second
  • 357 multiplications per second
  • 38 divisions per second
  • Programmable using switches and cables
  • Decadal (base-10) architecture
  • Thousands of vacuum tubes

This combination of speed and programmability represented a major milestone in computing evolution. Let‘s look under the hood at the technology that enabled this achievement.

Hardware Architecture

ENIAC used a decimal architecture based around ring counters and 10-position switches. Numbers were represented in base-10 using ten-digit signed integers.

The main components included:

  • Accumulators – Fast electronic registers that stored numbers and acted as operands
  • Function tables – Read-only memory units that enabled mathematical tasks
  • Master programmer – A central control unit that executed program steps
  • Other arithmetic units – Components for division, square roots, etc

In total, ENIAC had around 17,500 vacuum tubes, along with relays, capacitors, resistors and miles of wiring. The huge machine occupied a 30‘ x 50‘ room.

Technology Quantity in ENIAC
Vacuum tubes 17,468
Diodes 7,200
Flip-flops 70
Registers 10
Accumulators 20
Function tables 70

This electronic circuitry gave ENIAC its speed. The accumulators could process additions or subtractions in 200 microseconds!


Programs on the ENIAC were set up manually by manipulating switches and cables to route data and control signals between components.

Setting up a new program took days and debugging was complex. However, this programmability was a breakthrough over previous fixed-function machines.

Later versions of ENIAC incorporated improvements to the programming system, including:

  • Function tables used as read-only memory to store instructions
  • Insertion of a converter unit to input programs on punched cards
  • A primitive form of subroutines

Programmers could loop instructions and branch conditionally, enabling complex programs.

The Pioneers Behind ENIAC

ENIAC was a collaborative achievement, but a few key pioneers provided the vision and leadership:

John Mauchly – A physics professor at the Moore School, he first proposed building an electronic computing machine in a 1942 memo. Mauchly spent years advocating for the project.

J. Presper Eckert – The lead engineer on ENIAC, Eckert helped design and oversee construction of its revolutionary electronic systems. Just 27 when ENIAC was announced.

John von Neumann – The famous mathematician contributed to ENIAC‘s programming system. He consulted on the architecture and served on the review committee.

Herman Goldstine – A military liaison to the project, Goldstine secured funding from the Army and provided mathematical expertise.

Kathleen McNulty – She and other women "computers" from the Moore School programmed early test runs on ENIAC, despite lack of recognition.

Their combined talents allowed the team to overcome huge technical obstacles and create something entirely new.

Public Reaction and Long-Term Significance

The public announcement of ENIAC in 1946 sparked excitement about the dawn of the computer age. The New York Times called it an "electronic speed marvel."

Though not yet reliable or easy to program by modern standards, ENIAC previewed the potential of electronic computing. Among its long-lasting impacts:

  • Showed high-speed digital electronics was viable for complex calculations
  • Proved programmable, general-purpose machines were more flexible
  • Was adapted to handle early computer graphics
  • Inspired a generation of inventors to advance computer designs
  • Fueled the postwar technology boom and electronics industry growth

Both Mauchly and Eckert went on to form the Eckert-Mauchly Computer Corporation, a pioneering computer company.

For the first time, government and the public glimpsed computers‘ immense future capabilities across science, business, and communications. The ENIAC legacy continues today.

The Evolution of ENIAC: Key Versions

Like all pioneering technology, ENIAC went through many revisions and upgrades during and after World War II:

ENIAC Version 1.0

This was the original machine completed in 1945. It contained all the core electronic circuits and could be programmed through cable connections and switches.

programmed ENIAC (1946)

In this version, programmers implemented a form of read-only memory by utilizing the function tables to store instructions as digital patterns. They set the function table switches to encode programs.

Short Code ENIAC (1947)

The shortcut commands implemented allowed abbreviated programming. Looping, branching, and subroutines were possible. Richard Clippinger developed this system based on John von Neumann‘s suggestions.

Card-Programmed ENIAC (1948)

A converter unit was added that could read programs punched on standard IBM cards and load them automatically. This was a huge improvement over manual programming.

Register Panel ENIAC (1948)

This upgrade sought to expand the memory capabilities, but the hardware register panel didn‘t work reliably. However, a master programmer unit was added for better control.

Over its operational life, ENIAC was continuously modified and improved as a prototype computer. Lessons from its strengths and limitations directly fed into the next generation of computers.

Looking Ahead at ENIAC‘s Legacy

I hope this guide has brought you up to speed on ENIAC – its wartime origins, electronic circuitry, programming, key figures and long-term impacts on the computer revolution.

Here are some related topics if you want to dig deeper:

  • ABC Computer – Explore this early effort at an electronic calculator
  • Colossus Computer – Discover how this codebreaking machine helped crack German ciphers
  • The Women of ENIAC – Learn about the overlooked female programmers
  • From ENIAC to Microchips – Trace the evolution to today‘s computers

Let me know if you have any other questions! I‘m happy to share more about this fascinating innovation that transformed technology forever.