History of the computer

The first computer

One of the most frequently asked questions, about the history of the computer is "When was the first computer created ?"

While you would expect this is an easy question, this is not the case. That's why I will give you two answers - short and long. It all depends on the definition of what a computer is?

The long answer

A computer, after all, is something that helps us with computing. For that matter some people say that the first computer was a mechanical device, created back in the 1800s. Other people will go further in history to explain that thousands of years ago people used other simpler devices to help with calculations.

When I ask the question, I expect to hear when the first electronic computer was created. Such computer that follows common ideas and architecture with the computers we have today.

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The long answer continues

As you will see, the computer as we know it today wasn't created in one day, year or even a decade. It evolved with time. Many machines showed new features and ideas. Many of those ideas where useful and were adopted in future projects. Just few examples for such inventions:

Evolution of some ideas:

  • making the computer programmable
  • using binary logic
  • creating separate processing unit and memory
  • creating a random access memory

Technological evolution:

  • mechanical logic → electronic logic
  • using vacuum tubes → transistors → integrated circuits → ?
  • Input/Output Interface – punched cards/magnetic tape → keyboard, mouse, display,printer

and so on.

In this respect, looking at the history of the computer, there is not such thing as “the first computer”. BUT, I know you expect an answer, so here we go...

The short answer

The first electronic digital computer was the ABC (Atanasoff-Berry Computer). It was created between 1939-1942 by professor John Atanasoff and his graduate student Clifford Berry.

History of the computer - Ages of the Vacuum tubes

The Z1

In 1936 Konrad Zuse created the Z1. The first electro-mechanical computer.

Although we don't consider it to be the first “true” computer, it introduced many ideas that were used in other projects. Also its descendants Z2, Z3 and Z4 became better and better and Z4 became the first commercial digital computer.

Key features. The Z1..

  • was electro-mechanical
  • was programmable
  • read instructions from 35mm punched tape.
  • used boolean logic and boolean floating point numbers


The ABC (Atanasoff-Berry Computer) was created to solve systems of linear equations. In 1940 the two creators described in details the new machine in a document “Computing machine for the solution of large systems of linear algebraic equations”. And the next year, in 1941 they created the manual.

The computer had more than 300 vacuum tubes, weighted more than 320kg (700 pounds) and it had the size of a desk.

ABC featured new key concepts.

  • For the first time in the history of the computer vacuum tubes were used. Up until then, calculations were done, using mechanical modules likes switches, wheels and others.
  • It separated the memory from the computing logic.
  • As you can see in the manual above, it uses binary number system and binary arithmetic to represent, manipulate and handle the data.
  • Introducing regenerative capacitor memory. John Atanasoff came up with the idea of using capacitors for the memory. And yes, even today the RAM of your computer (or smart phone) consists of billions of capacitors.
  • The ABC used parallel processing.

However the computer was designed to do a fixed task and was not programmable.

Harvard Mark I

The Harvard Mark I was completed in 1944 by IBM. Howard Aiken had the idea for that machine for a couple of years before he managed to convince IBM to create it. The original name was ASCC (Automatic Sequence Controlled Calculator).

Although, it was rather mechanical than electronic, the Mark I introduced the Harvard architecture. It uses separation of data and instructions. Most of the modern processors today, use different modified versions of the Harvard architecture.

The Mark was a huge machine – over 4 tons (10 000 pounds) and consisted of more than 700 000 components.


The ENIAC (Electronic Numerical Integrator and Computer) was completed in 1946 by John Mauchly and John Eckert. The ENIAC was the first programmable electronic digital computer capable of solving wide range of computations.

It was created for the US army, to calculate ballistic trajectories.

At the time it was the fastest computer, ever created. t contained more than 17 000 vacuum tubes and weighted more than 27 tons. That machine consumed the amazing for that time 150 kW. The ENIAC used punched cards for input and output.

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