Mr. Claude Shannon. The Prehistory of Unix Part Five

Estoy escribiendo este artículo en una casa ubicada en el borde de la capital argentina. Cuando lo termine viajará por kilómetros de fibra óptica hasta la localidad balnearia de Las Toninas donde un cable subterráneo lo llevará por debajo del Atlántico por el camino más rápido hacia los servidores españoles de LinuxAdictos. Al publicarse, podrá leerlo en su smartphone el pasajero de un bus en Madrid y en su tableta un paciente sentado en la sala de espera de un dentista de Ciudad de México. Es posible que al primero le guste tanto que llamará a su madre para pedirle que lo lea, mientras que al otro le parecerá tan malo que subirá un video a Instagram diciendo cuanto lo odia.

The role of Bell Labs

Most of the technologies involved in the process, from the moment I turned on the computer to write the article, until the Mexican pressed the button to upload his video, originated, improved or were inspired by the work of a single institution. Bell Labs.

Funded by a small charge on telephone bills from the AT&T communications monopoly, Bell Labs brought together some of the best physicists, mathematicians, chemists, engineers, and other specialists in disciplines to improve or expand technology service.

Although what justifies this series of articles It is the invention of Unix, the operating system that Linux, FreeBSD and macOS were inspired by, transistors, cellular mobile communication networks and CCD technology for digital image capture also came from there. It is true that they did not see the potential of microprocessors, but the invention of these would have been impossible without prior research by laboratories in semiconductor materials.

Although Bell Labs worked with mechanisms similar to those of the free software communities and most of the inventions were the result of the collaboration of several people, perhaps his greatest achievement was an individual contribution. And, it is not a technology but a theory. Let me introduce you to Mr. Claude Shannon.

Mr. Claude Shannon

The son of a merchant and judge from a rural town and of a school principal, he grew up assembling and disassembling devices. His career in the world of communications began building a telegraph. From the first moment, his professors would classify him as a scientist with great talent and, years later, Albert Einstein himself would classify him as “brilliant”.

The first milestone in the story we are telling is when Mr. Claude Shannon, about to finish his undergraduate degree at the University of Michigan, sees an ad calling for operators for the MIT “differential analyzer”.

Considered one of the first analog computers, the differential analyzer took up an entire room and had to be operated by several people. He was capable of solving complex mathematical problems with a speed greater than that of any of the alternatives of the time. The machine consisted of a circuit of electronic switches that controlled sets of rods, pulleys, gears, and rotating discs, which operators had to constantly manipulate to match the values ​​in a numerical problem. The funny thing is that the analyzer gave the answer by writing with a mechanical pencil on graph paper.

Fascinated by the machine, Shannon became interested in the electromechanical relays within its control circuit. These were magnetic switches that clicked open or closed when a current was applied or cut off. The open or closed position of the relays could represent a yes or no answer to a question. Also, a chain of relays could branch in a logical direction representing the alternatives "AND" or "OR" depending on the open or closed positions.. That way, you could answer a complicated problem or run a complex set of commands.

Working with the differential analyzer gave Shannon the seed of an idea for a new way to design and use these circuits through the application of Boolean algebra.

Topic that will remain for the next article

The prehistory of Unix
Related article:
The prehistory of Unix and the role of Bell Labs
Bringing scientists and engineers together
Related article:
Bringing scientists and engineers together. The prehistory of Unix. Part 2
Vacuum tubes
Related article:
Vacuum tubes. The prehistory of Unix part 3
The arrival of the transistor
Related article:
The arrival of the transistor. The Prehistory of Unix Part Four

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