Alan Turing was one of the most influential computer scientists of the 20th century. Not only is he a scientist, but he is also a renowned mathematician, philosopher, theoretical biologist, logician, cryptanalyst, and a war hero.^{1}

Despite his many talents, the general public is largely unaware of Turing’s contributions to science and society. His works span many disciplines, including biology, mathematics, cryptography, and, most importantly, the early development of artificial intelligence. Without Turing’s work, computers as we know them today would simply not exist.

Popularly known as the “Father of Theoretical Computer Science and Artificial Intelligence,”^{2} Turing was the first to provide a formalization of the concept of algorithm and computation with his machine, called the “Turing Machine,” which is considered a model of a general purpose computer. In fact, the Nobel Prize in computing, the prestigious Turing award, is named after him.

Let’s look at the story of how Alan Turing built the first computing system in the world.

**How it All Began**

Though the idea of a programmable computer had been around since the time of Charles Babbage, who formulated the idea of his analytical engine, it was Turing who first did the hard work of mapping out the physics of how the digital universe would operate.

It began as a part of his attempt to solve a puzzle known as the “Entscheidungsproblem.” For many mathematicians at the time, this mouthful of a problem was a source of distress. They were attempting to determine whether they could prove any given mathematical statement to be true or false using a step-by-step procedure; an algorithm, as we would call it today.

Alan Turing tried to formalize how we compute everything from real numbers to functions, to work out the “Entscheidungsproblem” and conclusively proved that the problem is unsolvable using the Turing machine. To solve the problem, they needed a formal explanation of computability, which eventually became the Church-Turing thesis.^{3}

**The Turing Machine**

Turing was a polymath of the highest order and has left a list of achievements stretching far beyond the realm of computer science. However, the “Turing Machine,” invented by him while he was a mathematics student, is one of his most significant achievements. This Turing machine is one of the core concepts of theoretical computer science.

It was during his years as a mathematician at King’s College, Cambridge University, that he first published his seminal paper, “*On Computable Numbers.*” Though we consider the paper a key work in understanding the foundations of mathematics, his method, however, relied on a thought experiment. This exploration pushed him to imagine a machine that ran on instructions printed on a tape without being limited to what could be mathematically or logically proven.^{1}

Turing imagined a machine that could read both instructions and data from a paper tape and write back to it. This was the first prototype of a computing machine known as the Turing machine, which is used as a mathematical representation of a computer even today.

This machine was far ahead of its time, and while it would be many years before the “Turing Machine” could be engineered into reality, Turing’s idea for a hardware that could be programmed to perform different tasks is literally the basis of every digital computer in existence today.^{4} Therefore, Turing was the first to articulate the hardware–software distinction, which is now a key concept in computer science.^{5}

Though the machine he envisioned was still decades away, his brilliance, however, was noted by the British government. This leads us to the next topic of how he got to be known as the code breaker.

**Breaking the Code**

When the war broke out with Germany in 1939, Alan Turing, along with some of the smartest people of the time, was taken on board at Bletchley Park to face the seemingly unachievable task of breaking the Enigma code.

This phase of Turing’s career was his long foray into cryptography as he worked for the British secret service during World War II. The Enigma code was a sophisticated electromechanical device used by the German military to encrypt their top secret military orders. Turing played a leading role in the breaking of the codes, including those that were transmitted to the U-boat, wreaking havoc on the Atlantic shipping lanes.

The sets of rules for coding messages used by the Enigma would constantly change. So, Turing designed a machine that could cycle through hundreds and thousands of Enigma settings to match the available frequently occurring words across messages to identify the correct key. Turing’s contributions not only helped in the decryption’s success, but also played a substantial role in the allies’ eventual victory.^{6}

**The Development of the First Modern Computer**

After his pivotal role in defeating Germany, Turing helped in the development of two of the first modern computers. He began by describing his desire to build a mechanical brain, leading to a distinctly computational idea.

Though his theories about artificial intelligence were met with severe skepticism because he spoke of a machine that would one day be intelligent, we now know that what Turing offered at the time was the foundation for artificial intelligence that we have today.^{7}

As computers have evolved and become more important in today’s world, Tuning’s paper “*Computing Machinery and Intelligence*” has become a cornerstone of artificial intelligence.

In “*Morphogenesis,*” his last paper, Turing describes a mathematical model that can explain the development of biological forms or structures. He stimulated this model on the computing machine to prove his point and showed the forms that it could give rise to. This is the first step towards artificial intelligence, and his work represents an early instance of artificial life.^{1}

Though it took decades for Turing to receive the respect and honor that he never received in life, today, we owe a lot of what has happened in the advancement of computer science to his professional legacy⏤a legacy that is most clearly seen in the digital age that Turing helped create.

If you found this article interesting, go to BYJU’s FutureSchool blog to read more such amazing articles.

References:

*Alan Turing | Biography, Facts, Computer, Machine, Education, & Death | Britannica*. (n.d.). Retrieved April 11, 2022, from https://www.britannica.com/biography/Alan-Turing*Alan Turing | The Royal Society*. (n.d.). Retrieved April 11, 2022, from https://makingscience.royalsociety.org/s/rs/people/fst00117605- Brodkorb, L., & Epstein, R. (2019).
*The Entscheidungsproblem and Alan Turing*. *Wolfram 2,3 Turing Machine Research Prize : What is a Turing Machine?*(n.d.). Retrieved April 11, 2022, from https://www.wolframscience.com/prizes/tm23/turingmachine.html*computer – The Turing machine | Britannica*. (n.d.). Retrieved April 11, 2022, from https://www.britannica.com/technology/computer/The-Turing-machine*How Alan Turing Cracked The Enigma Code | Imperial War Museums*. (n.d.). Retrieved April 11, 2022, from https://www.iwm.org.uk/history/how-alan-turing-cracked-the-enigma-code*Alan Turing: The experiment that shaped artificial intelligence – BBC News*. (n.d.). Retrieved April 11, 2022, from https://www.bbc.com/news/technology-18475646